To clarify, don't think of the base building so much in terms of it being ground-based or space-based. Think of it more in terms of the actual tedium of the structure placement. Do you have to hand-place each individual factory, defense turret, and radar station, or is the entire base just a big, arbitrary mass?
In Starcraft, TA, SupCom, etc. you have to hand-place all your base structures. Adding to the tedium, you have to give the order to some type of builder unit. (Command and Conquer didn't have builder units, but you just placed structures where you wanted them). Regardless, you have to perform hundreds of mouse clicks to get a base looking the way you want it to.
In Civilization, GalCiv, etc. your "base" is a city that you simply order upgrades, research, and resources from. You don't have to mess with individual structure placement because that would be too tedious. The base more or less runs itself with you guiding it occasionally.
I'm guessing that in Sins the planetary bases are handled like they are in GalCiv, which would be a superior solution for a game of this scale. The orbital bases (the ones that can be engaged in combat) are what I'm wondering about. Do you build them up in real-time like any RTS game or do you treat them as abstract concepts? Basically, do you have to micromanage the base construction, or is the majority of the micromanagement focussed on the tactical fleet combat?
Whew, sorry about that being so long-winded