Found some pretty sweet info found in the Beta's code : http://www.360zone.net/halo-reach/18....html#post3572

Take your party to combat and objective-based missions that you select and design. Your rules, your maps, your game.
Campaign maker? Seems pretty feasible to me, since I remember it being said in the first ViDoc that the AI wasn't going to be scripted whatsoever. The Shield Generator armor ability sounds quite a bit like a bubble shield to me.

Also, Golf, Soccer and Bumper Cars gametypes? Sounds pretty interesting to me :P