Observation balloons, moving front lines, game within the game (even in an empty arena), WW1 ground war
What this should add to a 3 cornered war: Air base movement is not affected so land grab only moves the spawn points, and the front lines will always be in contact with the other 2 sides, just closer or further from their airbase. This will allow as many fun milkruns as a person could manage, without porking the game play for their enemy counterparts. Strategy may at some later time come into play, once members have found the sweet spots for gun placements, etc. Firing artillery at enemy lines and enemy guns, could make for some good MA practice.
Actually, tons more of things that just didn't hit me right off the top. And I haven't even mentioned the fun factor of Zeppelins and observation balloons.