Ooh ooh! I've got it! A Warhammer 40k MMOFPS!

Just imagine it: You're a soldier in a space marine/chaos/eldar/ork unit taking part in an invasion of a certain planet. Unfortunately, shortly after you land, a warp storm or whatever the hell you call those things overcasts the planet and you can neither call in reinforcements nor leave the planet. You're completely cut off and have to make do with what you have. The game would rely extremely heavily on squad-based tactical PVP, but would have a few quests to create a context behind the fighting. At the end of the last quest the warp storm subsides and you are able to board transport ships, and once you get on, you have the option of switching to another server (called "planets" in game, so essentially you're flying to a different planet).