What about a commander that would play the game like a RTS, sending on screen positions and orders to his soldiers. That would be very cool and entertaining, specially on strategus.
That could be a global commander or a squad leader, like the flag system we have now. Also with the new game mode you re planning, we could see interresting results for the placements of fortifications, he would place a ghost structure, and the players would need to build it, etc.