^ I think co-op would cripple an rpg to be honest. Either the second player would be totally superfluous or they'd mutilate the single player experience to shoehorn it into the game.
I do like the idea of the Firefly-esq format, but they're still need to be a central plot and arcing story. It can't all just be about getting work and choosing between being an "honest" smuggler or a cut-throat pirate. Basically you'd need something to give you a reason the keep playing other that an endless series of sidequests.