Sure. It would be an FPSRPG hybrid in the vein of FO3(with more FPS focus)
You play joe alien starting from the moment you arrive on the ship (small tutorial on board) Then your whisked away to D9. There you fight for survival amongst your fellow prawn the Liberians and the PMC guys. You can chose to do missions for either group with an overarching story of return to your home(at least the ship). And throughout the game territory is controlled by different factions or prawn PMC and Liberians so your alignment with a faction effects your access in D9.
The faction quest would be to be an informant for the PMC (ie find weapons/illegal caches and report) this would be a pseudo stealth branch to the game. And this would tend towards a neutral alignment (ie whats best for you) In this line you would earn a lot of assets money/house/safety/weapons. Plus the PMC would look the other way with whatever you do.
You could work for the liberians and deal in the arms trade. This would be the thug or bad side. Imagine a quest where a group of prawn fail to pay for weapons or food/supplies and you go to their place and "enforce" the bargain. Or you just flat out steal things to trade or just, murder and pillage.
Or you could work for the "leader" prawn for the greater good. Here you collect the things you need for the return to your ship, you could recruit people, you can engage in skirmishes against the Liberians or PMCs. This would be the good quest line and you would gain more access to technology.
Now imagine gameplay. In the begining you have nothing, no alliances or weapons. You would fight fellow prawns for things/survival. It would be melee intensive combat Picture walking through the "wrong" part of D9 or taking someones food and being assaulted by prawn you would fight chronicles of ridick style IE with whatever is at hand wrench/pipe/2X4/shiv. Here in this first 20% of the game you would be introduced to the factions gameplay and environment.
Now say you've chosen to work for the liberians and your rep is low with everyone else. You would have the PMC pissed at your actions and you would be a wanted man. They would be hostile and try to arrest/kill you on sight. Perhaps your fellow prawns, enraged by your manipulation of them would scheme to ambush you. Same goes for working with the "leader" prawn or the PMC both would have consequences in gameplay.
And throughout the game there would be set climactic events. Say a PMC massacre, tanks and helicopters and soldiers are pretty much murdering prawn so you have to fight back on a large scale.
Or a Civil war amongst gangs of prawn.
Not to mention the overarching story and the set pieces in that.