Isn't the main concern with multiplayer rules how to stop ganging up? Isn't a simple solution to this to say (speaking in terms of team-based games) that 2 or 3 zones need to be burnt, with a minimum of 1 from each opponent?
Then turns simply switch between a player, followed by a player from the opponent team, then the OTHER player from the first team etc'... with attacking still being the simple selection of zones, but with the added option of which player to attack?
Cheers