Sorry but no, I don't think very much of the idea as you've laid it out.
While there should be other optinos for gameplay other than 'kill-em-all' the ones yu've listed aren't very workable. I like the idea of being a bounty hunter or a trader as a part career but I don't see how there could be enough in it to warrant a whole class let alone a faction.
I think you'd be better off trying to get similar features added as gameplay available to everyone. Side missions and features for trade and bounty hunting would work fine - just like diplomacy missions/features have been added.
Lastly I can't see any way in which colonisation would make for interesting gameplay relevant to the rest of the game. I know they've added planetary interaction in EVE but thats a whole different type of game.
Edit: Ooh I just thought of something - maybe we could build colonies of Orion slave girls and then trade them to players - like tribble breeding only sexier!
Why bother writing something that will never be implemented? Do you really think they have enough people to work on something so pointless? If youre going to suggest an idea, make sure it is easy to implement, otherwise it will never see the light of day.