[JThur]

What about space ship colonies? I've always wanted to play a locust race in space strategy games where your race mainly live on ships and go from star system to star system and reap the resources as they go.

Game wise I guess it would be like a race with movable planets of varying sizes that either colonize existing planets and make them movable or build movable planets from scratch with lots of resources.
It would probably be a good idéa to give them organic or energy to matter tech so they can build some resources if they run out of resources to loot. Superb storage tech would also help to tone down the aggressiveness and blunt the damage if they get stalemated a bit.