One annoying thing on larger maps, when playing with teams, is that when your ally at the other end of the map meets another race, like the Drengin or the Yor, they will declare war on you in the next few turns.  Then you wait until they finally decide to come at you.  300 turns later.

Why not have a white peace, where all belligerents are forced into a peace situation if there's no hostile actions for X turns?  Say, somewhere between 50-100 turns (it needs to be evaluated), it might give the AI a better chance at conquest by having it focus on its immediate neighbours instead of trying to build a bridge to reach me while it gets pounded by the other AI.