What you can't do though is have more than 2 players, otherwise during a battle the other players will be waiting for ages before the next turn.

Star Wars Rebellion was before Empire at War (LONG before) and had turns ticking by at a rather fast rate, it was similar to the map interface on Empire at war and had a 2 person head to head. The only fighting you did was with the other player.

This wouldn't work as well with a Total War game though because the diplomacy is half the fun on the campaign map, there is nothing so satisfying as knocking off a nearby nations general without them knowing. Though I would still be overjoyed if someone did implement some form of campaign multiplayer function.