The allies command allows you to set two AIs to not attack each other. Here is a short-list of map commands.
http://www.dom3minions.com/docs/map_qref.txt
With #allies you can create a map as a scenario such as
A) F.E.A.R
the Family of Ermor, Atlantis, Rlyeh. 3 pretender gods, all siblings. They have agreed to share the world. Start them with extra castles and armies and equipment.
B) Save Arcos
Set Ermor as "ally" to Arcos just so it wont attack. But place Arcos inside its castle and Ermor outside of the castle, seiging it. Your mission is to get there and free arcos before they fall.
C) Turtles
Give all of the AIs 5 or 6 starting provinces and set them all ally to each other. Including possible setting them ally to nation 23 (the independents). That way NONE of them will attack. They will only sit and buildup wating for you to come and get them. Might create some fun giant battles.