As a fan of other games of this genre, I'm eager for a new SOASE race to play. Going through the posts, I saw there was some popularity for 'the robots' as a 4th race. I totally agree. So here we go, a new thread with some real ideas about the who, what, why, and how regarding the robots.
INVASION (proposed mini-expansion for SOASE)

Backstory
The proposed robots are intelligent artificial lifeforms who wield advanced tech. Long ago, they were created as 'Servitors' to an ancient star-faring race. It is a complete mystery as to the fate of those they served. All we know is that the Servitors are on their own, motivated by complex programs and mission statements which they might have learned to write and revise.
Next to nothing is known about these Servitors. A very incomplete TEC study of intercepts of their machine language suggests that, long ago, they met with one or more intelligent species who 'altered' their ways of thinking, and possibly sent them in this direction.
The warring races locked in the current Entrenchment War are still scrambling to collect intelligence about the unexpected invaders. The Servitors appear to have nothing to do with the current drama played out by the TEC, Advent, Vasari, and the entities pursuing the Vasari. They rapidly descended upon this resource-rich sector of space after centuries of travel across the great void between spiral arms of the galaxy, arriving here and there without warning. Their unbiased, general hostility illustrates their goal -- to invade and harvest the resources of the sector, eradicating any and all opposition in the process.
What are some things which would make them unique and fun to play?
1. They do NOT colonize planets, and have little need of them.
2. They are nomadic. Their equivalent of planets are 'Worldships' which are basically mobile starbases which can jump from planet to planet, system to system, when upgraded. Aside from the first, each worldship must be built and continually expanded. Each frigate/cruiser factory is built within a Worldship, thus their fleet construction is mobile as well.
3. Their populations don't 'grow' as organic life does (by colonizing and inducing population infrastructure). Their populations (worker units) must be 'built' on the worldships, and thus cost resources.
4. Edit. Requiring only small amounts of Crystal, the main resources they hunger for are Antimatter and especially Metal. As such, they are naturally attracted to metal rich planets, asteroids, moons, etc.. They are also attracted to stars - to harvest all the rich solar energy. Once they gain enough resources and research, they can construct special energy production installations (i.e. Singularity Tomb) to gain additional antimatter.
5. Culture is of little concern to them, and has no effect on their civilization; although they may seek to employ technology to harm other empires via cultural broadcasts.
6. Also, trade and credits have no relevance in their society.
7. They have many different types of technology. They don't so much as 'research' new tech, but awaken and reactivate old systems long depleted by their great wandering in the void. Some main specializations involve transportation, infiltration and covert activity, efficient industrial activity, and manipulation of exotic dimensional energies. Their need for examining, analyzing, and observing other races -- often covertly -- is as vast as their appetite for resources. Their jump drives are based on tech very different from the others. While slower in speed, requiring slightly longer to charge up, their drives don't have to exit a grav well to initiate. They may also be upgraded to be immune to jump 'radar'.
8. They are a collective. With no concern for individual personal safety, the Servitors have a different brand of warfare, with techniques and technologies that may cause damage to their own forces as they damages the enemy. This may involve suicidal ram-ships, Nova-ships, Singularity Inducers, and powerful over-charged cannons that burn their own ships in the process of destroying targeted enemies.
9. They have some exotic technologies which involve cloaking, temporal manipulation, black hole and wormhole creation, data-network infiltration, advanced replicant spies, tractor beams, 'Locust' hull eating, shield manipulation, and so forth.
10. They scavenge space battlefields with precision, sucking up metal with Jackal ships. They may also cannibalize their own ships rapidly and efficiently in order to accumulate emergency resources to make others.
What would be some of their weaknesses to balance them out?
1. The Servitors have most of their eggs in just a few baskets -- the Worldships. They have to struggle to build as many as prudent and develop them continually -- all at massive development and maintenance costs. Worldships are slow and thus can be trapped. Only one may inhabit a system at once, due to problems with conflicting network protocols and hardcoded algorithms dictating dispersal of command.
2. Since the SLOTS -- equivalent of Population Infrastructure, Emergency Facilities (heavier hulls), Logistics, and Tactical -- are built within each Worldship, damage inflicted on the Worldships will randomly destroy these slots within. Also, some Tactical slots are within the Wordships too. Same thing.
3. Since the Servitors have little interest in trade, credits, Culture, alliances, the black market and pirates, etc.. they suffer the many potential consequences.
4. Denying a Servitor fleet access to Metal and Antimatter could really limit their 'Invasion'. It's one of their Achilles heels.
5. The Servitors can cause a lot of damage, but may also damage themselves in the process (depending on the ships).
6. Repair, maintenance, production, and expansion is all costly.
7. Their transportation methods are different and initially slower until drives and engines are incrementally upgraded. Once they get enough development and resources, they can get back to the powerful speeds with which they began the Invasion.
8. While they are learning to counter them, fighter and bomber are not their thing. They don't build them. No don't have light carriers or hangars. They do, however, have alternative methods available to make counters vs fighters and bombers.
9. When they want to build orbitals in newly conquered systems, they don't just 'do it' because they don't colonize planets. They must build and send Constructors and Heavy Constructors. These constitute an Achilles heel too, since enemies may focus on destroying constructors.
10. Since frigs and cruisers can only be built in Worldships, frig/cruiser production will limited to and contingent on the number of expensive Worldships which can be built.
More ideas coming when time permits -- ships, orbitals, special abilities, misc... The point will be make something DIFFERENT yet not UBER, so they can fit in the game with enough refinement and brainstorming.
In the meantime, feel free to add to the ideas, question, or criticize. Thanks