This one I have thought of for a very long time. Working out all of the specifics could be challenging however the result could be amazing.
Imagine a system where you could enter a closed tournament and it automatically pages you when its time to play. My thoughts would be to integrate a GB style tournament into matchmaking. This could have so many applications and matches in tournaments could be scheduled on certain days. Maybe play for Microsoft points for the more adventurous?
Like I said there would be a million variables to this idea but I think it could be an unbelievable feature in the game.
SaiNts