How about this idea?
Imagine a BTB game which lasted a lot longer than the twelve minutes or so they run at present.
Such a game would last an hour or even longer.
Players would be removed from the game every fifteen or twenty minutes - acting like time out of the front lines (R&R) in real combat - but during that time away from the BTB Big Game would still be able to go into SO or Campaign or other Slayer-type games. When they did rejoin the original game they would rejoin their original team.
Join in Progress would unfold automatically, keeping both teams at at least 75% strength and the teams would increase from eight to at least twenty a side.
Such big teams would necessitate much larger maps with the use of airborne fighting vehicles - not just Banshees but Hornets as well as Falcons.
Objective type games would shine here - imagine having to defend a base while under prolonged siege.
Tactics would count - you could board half-a-dozen of your team-mates into a playable Pelican to operate a flanking manouver or 6 could clamber aboard three Hogs to raid an enemy base.
What do you reckon?
Could it be done and, if it was, would you want to play it?