Hi Biddy,
no ai is needed for these factions; the ai would mix them in a very ugly style - in singleplayer you simply put all enemy factions to the opposing team. You will still meet mixed hosts, but there will be some basic order; only a human player can manage these superfactions to his likings, the ai will never do it.
What is your system for the ring heroes ? It kind of annoyed me to hunt for the Ring in each map, and to build Sauron all the time. So I just made him a super expensive and long recruiting hero for Mordor. No, it is not fair :-) but it is fun. Maybe if there was some possibility to restrict his recruitement (and the one of the Balrog), it would be great. But I did not figure it out.
MoS