What about a system for capturing lifeforms and then you can choose what to do with them. You could store them in your ship and move them to another planet, to see how they would cope. Or perhaps sell them to on a market and earn cash depending on how rare they are. Stuff sold to the zoo could be viewed by other players, social network, player profile or even in game by visiting multiplayer players.
Hm... What if i would choose to sell an NPC? He's a life-form too. It would make... A slave market? Would that be possible? Of course it would be illegal and you would be chased afterwards, but the ability to sell people would open up new quest possibilities - for example intercepting slavers and freeing their cargo, fighting poachers and etc.
