Space marines of the 41st millenium
I'm gonna try a different tack with this game, assuming it ever happens: I'm gonna lay out the plan ahead of time, so that everyone knows what the game is about, instead of challenging the players to discover that on their own.
The Big Idea
The idea here is that the bulk of the players are Space Marines: roided out, superhuman killing machines, one unit of a few that are stranded on a bombed-out hive-world colony, trying to preserve the people that are left, and fight off an alien menace, and at the same time try to preserve what society is left on the planet. Likely the planet will have its secrets, as well...
I'd probably set this game in the WH40k universe, on a planet stuck in the Maelstrom, so the players would be from one of the chapters of marines that's more like grizzled special forces, and less like fanatical crusaders.
The central core of the game wouldn't be combat, though it'd happen. It'd be the fact that the players are highly trained killers, but their relative power makes them the defacto leaders of the planet. Sure, a Navy SEAL is great at killing the hell out of people - is he so great at talking down the family of someone killed in the crossfire? Is he good at ensuring the peace? Can he keep a society stable without going native?
The Rules
I'd probably use the Warhammer Fantasy system for this game, but allow people to choose careers from a set that I make. Most people would be race Space Marine, which is great at combat, but not so much other things, and one or two people could be civilians.
Space Marines | Space Marine Careers
Experience
Everyone would start with enough experience to immediately advance from their first career.
The Setting
The setting would be a world in the Maelstrom, so cut off from the Imperium at large. Furthermore, they'd be crash-landed on a planet with no real hope of escape. I think the Marines in question would be Astral Claws, the chapter of Huron Blackheart, famous renegade, though the story from his side of things is a little different.
Since the players are stranded, equipment would be limited. To represent this without it becoming the focus of the game, I think I'd allow a certain amount of equipment use per session more or less without penalty, but extended use (say full-auto bolter spray, or several armor-penetrating hits) incurs a penalty to future freedom of equipment use.
