Turn limit option in game settings i.e. victory goes to players in order of most armies currently on board, or even most armies defeated over entire match (this would encourage more engagements) in the event that the game hasn't been decided after a prescribed turn count. You can adjust turn count limit in settings (e.g. 30). Enforced alliance treaties: you can agree to an alliance for a certain number of turns i.e. 1-10 but you are bound to the alliance and cannot (i.e. are unable) attack your ally's territories without express consent until treaty expires. The express consent (in the form of a checkbox popping up on ally's screen) would solve the problem of intervening territories you may have to attack during your campaigns against mutual enemies.