My problem, is it would make gameplay really repetitive. Some of the maps in this game are pretty big and well designed enough to support fighting all over it, a single MOTF will effectively cut off the vast majority of the map until the same scenery gets stale.
This will suck for flanking playstyles really badly as well.
Actually I think cav and flanking playstyles in general would get an advantage out of it, because flanking is pretty useless unless the attention of the enemy is directed somewhere else. The difficulties flanking playstyles are experiencing with the current battle setup is that people can avoid combat and thus stay aware of their surroundings for a much longer time, which renders flanking useless if you can only do it effectively in the last part of the battle.
Yeah I thought 30 seconds or a minute would be good.
I think the instant people can't spawn anymore would be a good choice.