Re-live Marathon:Durandal. Get it today for 800 Microsoft points on the marketplace.
I think this is a good idea. It would be kinda hard to make sure there arn't any glitches with spawning, but creating an AI system in multiplayer is far to great of a project... they only got a year left in development. If they were gonna do it, they probably already started, or decided not too.
I like it, but its not likely...