A bit late to the party on this, however I thought I'd put forward my thoughts on systems/design choices from Sins I that could be updated in the sequel. Most of this isn't focused on big sweeping changes, moreso on smaller adjustments I believe would improve the look and feel of the game, without changing its heart.

Most of this is based on observations of feedback from a decade or more ago regarding Sins I, as well as design lessons that can be taken from other games in the genre. I've split this into a few categories for easier readability (I am unfortunately a bit verbose), but there is some overlap between them.

Faction Asymmetry:

One area I would like to see updates to, and I've seen others suggest as well, is asymmetry between the factions. While the factions in Sins I did play differently, especially towards the late game, it didn't always feel like they did - especially early game and in lower tier play. Probably the best renowned RTS for its faction asymmetry, as well as one of the most popular, would be Starcraft II. Some thoughts for improving asymmetry from comparing Sins I to SC2:

Faction differences should start from the beginning of the game. In Sins I, the two main early game differences most players would note is the different capital ship options, and the Vasari scout's ability to cap neutral extractors. Beyond this, all races start off with the same basic options, and similar initial gameplans. In Starcraft, the very act of building your first structure is handled differently between each race, with the Terrans taking a worker full time to sit and build the structure, the Protoss placing a structure with a worker that then builds itself, and the Zerg transforming their worker into a structure. Other differences only continue from there, with different early unit comps, expansion timings, scouting methods and more. In Sins II it would be nice to similarly see early differentiators between the races; different scouting methods, different early ship purposes, different expansion goals and rates, and similar. The late game differences were always much more apparent, but it feels much more impactful having earlier differences too.

One of the other major factors that led to the Sins I races feeling very similar on the surface was the uniformity of options available to each race, at least until late game (And improved a lot with expansions). Every race had the same breakdown of frigates, cruisers and battleships, as well as most of their structures also being the same. This led to less unique thoughts for each faction like "My enemy is focusing on strike craft, I'll build [Faction specific counter]", and more generic thoughts like "My enemy is building strike craft, I'll build some flak frigates". Having a unique set of ship and structure purposes for each race would help differentiate them significantly. Along with this naturally comes having unique compositions and strategies throughout the game on how to handle your opponents.

One thing Sins I did well late game, especially with the expansions, was the factions having unique capabilities that the other factions did not. The Vasari being able to see all movement on the whole phase lane network, create their own network to ignore phase lane limitations, and add an enemy planet to it while disabling all their fleets and defences (Not even mentioning moving starbases, or being able to abandon planets completely) played and felt very different to the TEC's more restricted movement, but much tougher defences and ability to outright kill enemy planets without invading, while having constant rebellions annoy enemy factions. Keeping and expanding these factors I think is a must to keep factions feeling different into the lategame.

As just brief note, balancing asymmetric play can be difficult. The main way Starcraft seems to accomplish it, from patchnotes, meta and changes with updates, is a focus on tightly controlled timings in the early-mid game, with the late game being more traditionally balanced. Knowing what plays and counter plays each faction has against each other, a control of timings ensures that for any play one player makes, the other will always be able to make the appropriate counter play if they have adequate game knowledge and awareness of what their opponent is doing, and places more of a focus on both execution of the play and counter-play, as well as strategic decision making of which plays to make, allowing the incomparable options between factions to not be directly weighed against each other - only what those options can actually achieve.

Some very unpolished examples regarding this: The TEC may scout with dedicated ships, the advent with culture, and the Vasari with their phase lane technology. This would lead to very different approaches on how to get information for each race. Tech trees might also be different, with something like the Vasari having a very wide, but not very deep, tech tree - as they're near the pinnacle of technology already. Maybe they focus on improving specific structures and ships directly, rather than sweeping improvements to all ships and structures like the TEC with their newer military tech would need. Similarly, perhaps with their nanites, the Vasari only have one type of shipyard, that constructs all ship types at differing rates and volumes; 4 frigates, 2 cruisers or 1 capital ship could be built simultaneously. While obviously requiring more thought, things like this would lead to the individual races feeling quite different to each other in how they play.

Game Feel:

4X and RTS are genres that usually focus on opposite ends of the strategic scale, and Sins I did an excellent job of handling the user experience issues that arise from trying to bridge the gap between the genres. Many of these also added into the feel and fantasy of commanding an interstellar empire and its fleets, especially the fleet system and empire tree. With 15 years since these systems were developed, Sins II can be made better by incorporating newer advancements, and options tech may not have allowed for at the time.

First up, a quick look at the Empire Tree. This is a key feature in Sins 1 that allowed the player to easily see detailed information from across a wide empire at a glance, no matter their current focus or visual scale. At the time, and to this day, not many games had something similar, however games like Stellaris and the newer Terra Invicta have a similar bar to keep this information visible to the player. Honestly I don't think there's a ton that needs changing here, however minor improvements were added by each game. Stellaris ordered and categorised entries in the 'outliner' bar between different types of pinned object, and Terra Invicta added filters to be able to only display certain types of objects at any given time. These help the player focus on the most relevant information they're looking for at the time, and would help declutter the empire tree in the late game.

One area the pacing was a bit off in Sins I for me was in fleet battles. These could go on for a LONG time, especially when one force didn't vastly overpower the other in the late game. Individual battles of 20-30 minutes weren't necessarily uncommon, and early game a fight against an evenly matched opponent could take 5ish minutes to complete. Some level of slower fighting is needed to allow players to also manage their empire, rather than keep focused on the fight, however I'd keep early game fights to 1-2 minutes, mid game to 5-10, and late game huge fights to 10-15 minutes. Plenty of time for decision making, especially compared to the 30 second or so battles in something like Starcraft, but not quite as long as in Sins I. As part of this, I'd have especially capital ship active abilities have a high immediate impact, but on a longer cooldown. This allows a momentary shift of focus to use or respond to the ability, and then breathing room to focus on something else, while also making the abilities feel powerful and fun to use.

I also think some of the early game 4X gameplay could be sped up a bit. Planet garrisons were one of five or so factors restricting the player's ability to set up colonies and expand. While for certain key planets they provide a nice risk/reward decision for early expansion, there are also a lot of times where they're more just busywork than adding anything at a strategic layer. For major points of interest on a map, I'd keep them, however I'd otherwise skip them on unimportant planets like dead asteroids, or where another factor like technology is the major influence delaying colonisation.

Something that feeds off a different gamespeed is the intuitiveness of counters. Sins I did help players a bit here with outright stating counters in tooltips, however also important is having a counter feel like an impactful counter. In Sins I, a semi-common noob mistake I saw was the idea that TEC flak frigates are the best frigate for them, due to the high health, ok armour, and high potential DPS from 4 weapons. This intuition, however, is wrong. Because of hidden damage multipliers against different armour types. Longer battles hid this information better from players, with the DPS not being as easily visible to a player compared with quicker battles. This is also a similar situation to the Arc Emitter weapon in early Stellaris; it was listed as having 100% bypass of all defences, with middling but highly variable damage. This lead many to believe it was the best weapon in the game. In reality, it was one of the worst against anything but evasion; it made up only a small part of a ship's overall DPS, meaning all its damage bypasses except evasion were quickly outpaced by the rest of the ship's damage, and became pointless. Far more intuitive is the likes of the immortal from Starcraft II. Intended as an anti-armour unit, its attacks will knock out half a low-tiered armoured units health instantly, while doing little against an unarmoured unit. Similarly, its shields block large damage values common to armoured attackers, but do nothing against low damage fast attacks common to unarmoured units. Intuitively, the way the unit feels to use matches its intended meta use.

As a quick broad UI note, while I don't agree with all of the ideas or execution, some of the UI ideas explored here would be nice to see done properly in Sins II. Particularly the ability for the player to pre-set their faction's icon, portrait and colours in the profile (As well as the semi-custom nature of having different individuals and backgrounds available to make a composite portrait for personalisation), as well as the idea of a dynamic UI where parts of it will not be obstructing the screen unless a relevant unit/object is focused or selected by the player, and having both a map splash image, as well as the ability to see the layout of a map from the match hosting screen, rather than needing to open galaxy editor or actually play on the map to know its layout.

Finally, a common wishlist item for many back in early Sins was for more dynamic looking battles. Strike Craft and eventually Corvettes flew around the battlefield and made it look dynamic and interesting, however all other ships tended to sit in a blob/wall and shoot as a firing line at their opponents. More motion, and a greater range differential should be added to combat IMO. This adds more visual interest, and makes the fight feel more like a space fight, while also giving greater purpose to the side weapons of various ship types. Not everything should move similar to fighters, however a mix of different weapon ranges and speeds could result in a much more dynamic looking and feeling combat without needing the same fancy manoeuvres. I'll touch on this more in the next section, but some more movement and less firing lines in combat would be nice.

Combat:

Segwaying off the previous point, there were positives and negatives to combat in Sins I that I think could be iterated on to make combat look and feel more dynamic, while addressing some of the more boring or frustrating aspects that could arise in Sins I.

First off, combat ranges and speed. Increasing the size of gravity wells, and giving ships a greater variety in weapon ranges and speeds would result in more tactical considerations in a fight, with range and speed playing a more than marginal role, as well as adding visual interest to fights - helping with both quick readability and avoiding the 'static blob of ships' look that happened to larger Sins fights. I would envision a front line, mid line, and rear line. Front Line would be close combat ships like Light and Heavy frigates in Sins 1, meant to attack the enemy and focus down specific targets. Mid line would be screening ships, meant to protect the rear line and prevent the front line from breaking through, as well as some close combat support ships. Rear line is for your glass cannons like LRMs, as well as other support ships. Give a solid visual gap between each line, allowing time for reactions to movement between the lines, as well as to give a solid advantage to longer ranged ships. I would also have especially the combat capital ships have weapons with different ranges; short, medium, and long, and a range setting to choose where the capital ship would choose to fight. Engaging at the front lines would provide a large boost to DPS, but also leave the capital ship vulnerable due to a slow speed to withdraw if needed. Sitting it in the back lines it wouldn't add a lot of DPS to the fight, however would also be protected with opposing LRMs not being able to breach the front line of battle to attack it, and being closer to a phase lane if it needs to retreat. This would make how much you commit your capital ships to a fight an important decision to make, with the broader changes to range and speed providing an more easily readable battle with visually distinct groupings of ship types/purposes, and would add more movement into the battle as the front line constantly moves to focus specific targets or try to breach the mid line, while the mid-line would have slower ships that would take longer to position, and may need to reposition to respond to changes in the front line. Moving ships like capital ships between lines as they need to retreat or advance would also add visual interest, without needing all ships to fly as unpredictably as fighters or corvettes.

Something else that would be nice to see altered a bit is the alpha strike potential of strike craft. While highly expensive and impractical in competitive games, if a large enough stack of strike craft is gathered, they are able to one shot pretty much anything in a single flyby, while taking no economic damage as a cost - potentially just some time to rebuild a couple of bombers. This... isn't really fun, especially when the prime targets for such a strike are the capital ships a player has spent the whole game levelling up, and they are dead before being able to act. With their long range and high speed, they're also able to do this as a hit-and-run technique, dealing a lot of damage without engaging the enemy. Even if not an optimal strategy, the pain of the alpha strikes is not fun to deal with. I'd rather see strike craft become more of a long ranged, sustained low damage option. Something that chips away at an enemy before and during a fight, but isn't practical as a hit and run or alpha strike technique. Honestly, probably the only thing that can achieve this is penalising focus fire. Sins I did a pretty good job of this with shield mitigation, however some tweaks to further incentivise spreading out a fleet's firepower may be warranted. Removing the incentive to fully focus fire both makes battles look more visually interesting, allows casting and 'hero' units like capital ships to be used and not instantly die, and allows for a player to shift their focus from the fight to address the 4X side of gameplay easier, without worrying that an important ship could be focused and quickly killed while their attention is away.

A final consideration would be to make armour more than just a HP multiplier. One change that greatly improves the intuitiveness of battles is to reduce the number of armour types and weapon damage types to much lower numbers, removing a lot of hidden values that determine the effectiveness of one unit against another. This can lead to a homogenisation of combat units, however, as there is less they're able to differentiate themselves with. Different defence type behaviours, rather than damage multipliers, adds more natural differentiating factors, without hiding the mechanics of them. One common example is having shields regenerate fairly rapidly, representing a DPS check that a fleet must pass to be able to at all damage an enemy ship, while armour is a damage reduction amount, presenting a burst damage check that the fleet must pass as well. This means low damage high fire rate weapons are great against shields, but weak against armour, while high damage low fire rate weapons are the opposite. I don't know if this is how armour should be treated in Sins, however treating it differently than just a multiplier for ship HP makes a ship's actual durability more easily readable for players (No need for a somewhat complex calculation to understand a ship's actual effective HP), while allowing for more behaviour based counters, rather than combat multiplier based counters.

Campaign:

The last thing I wanted to very briefly touch on is the idea of a campaign for Sins II. This is a widely popular request, and matches market data that the majority of RTS (And probably 4X) players focus on single player offerings, rather than multiplayer. I have seen that there are no plans for a campaign in Sins II at launch, however this may be something to consider for an expansion.

One factor that was raised regarding a campaign is wanting players to be able to have their own stories, rather than there being one official story of this war that is cannon. I do think this is an important factor of the game that would be good to maintain. One way to achieve this while having a campaign would be to have a campaign similar to Offworld Trading Company, the Total War games, Rise of Legends, Battlestar Galactica; Deadlock, or the old Star Wars Battlefront II galactic conquest game mode.

Put simply, the campaign offers a strategic map, with the player being given a strategic goal based on what their faction is (TEC Loyalists: Defend the core worlds, achieve peace without letting them fall. TEC Rebels; regain all lost territory. Vasari Rebels: Escape to the other end of TEC space while allied to at least 1 faction from each race. Vasari Loyalists: Cannot ally other races, escape to far side of TEC space. Advent Loyalists: Subjugate TEC core worlds and main Vasari fleets. Advent Rebels: Defeat Advent Loyalists and reach a peace with other factions), but otherwise not having a set story to follow. Instead, the campaign serves as a source of official lore on certain locations and individuals within a faction, as well as providing a more in-depth 4X gameplay mode to connect individual normal gameplay skirmishes.

Depending on much work was to be put into this style of a campaign, the results could be quite different. On the lower end, you'd have a basic map of the territories being fought over, with the ability to move fleets to set regions with some lore tidbits for players to take interest in and start a normal Sins II match in those systems. On the higher effort end, you could have more in-depth conversion taking many of the 4X elements (Diplomacy, technology, planet development, fleet production) out of the skirmish battles, and either splitting it between the 4X campaign map and local maps, or transfering it entirely to the 4X map, with open ended quest chains for each faction (More as a guide on how to win the campaign, rather than set story beats), lore for both systems and some characters that could be used as advisors or fleet captains/region governors/faction leaders, and some unique maps that explore concepts and scenarios that may be novel for the occasional playthrough, but would otherwise be frustrating in a normal Sins match (Like a planet that disconnects from the phase network entirely due to orbits for a period of time; frustrating in a competitive match, could be more interesting as an isolated scenario).

This would address at least some of the desires of those looking for a campaign (More lore, the ability to lead the whole war, rather than isolated skirmishes, some connection between individual skirmises), without impeding the ability for them to tell their own story of the conflict through the gameplay.