Diplomacy AI MUST get realistic. I am not talking to get less aggressive. If factions see that can benefit from a sneak attack then they must do it. If they would better benefit with an alliance with another AI faction or the player then they should try to avoid conflicts. Diplomats of foreign countries should conduct the player much more. Its like the player is the only one to care for diplomatic relations.
I don't care for dipliomacy! But the AI should accept protecrates and ceasefires when they're being destroyed, not fight to the death, as mentioned earlier. Also, the AI should buy into the 'protection' racket. Whenever i say 'accept or i'll attack' the ai will either say they'll take their chances (against rome - come on) or that they dont trust me - and i've never broken any treaties!