each skirmish is simply a race up the tech tree.
I can understand how the game might not be enjoyable to some people, but that's a gross oversimplification. It's a bit like saying any RTS is "simply pointing and clicking".
On topic: Homeworld didn't have planets as fixed bases. Instead the mothership slowly upgraded its manufacturing capabilities as it moved from location to location across the galaxy, allowing the player to build more and better starships. It had an aspect of "growth" to it on each map that really helped the ability to tell a story.
Sins normally starts with in one single map and finishes with an empire.
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I could see a campaign easily making sense by using a set of individual maps representing solar systems and star clusters within an overall galactic sector. Each map comes with its own objectives, and as you advance through the campaign and the borders of your own territory expand and collide with other empires, the number and power of your enemies increases.
For example: TEC's campaign could have an overall objective to build an invincible economy by creating edge-to-edge trade routes. You'd start with a small easy map in an unexplored galactic cluster that had you wiping out garrisons and fending off a small Advent scouting fleet. From there, you'd send out colony frigates to other star systems (i.e. maps), each having its own objective and special considerations. One might have a lot of resource asteroids that you have to claim, another might require you to annihilate a particularly powerful pirate lord, and so on.
Vasari motivation is collecting resources and rapidly moving on while keeping a fleet of colony motherships alive. Advent's story might be spreading their culture to the heart of the TEC empire to create a civil war and reclaim a secret culture-producing artifact technology that was left behind.
Such a campaign would be *long*, but I'd sure play it.
-- Retro