This thread is getting very confusing .....
You talk about AI behaviours, CPU fighting strategies and balance and even more .... Please stay with one thing.
But for the balance thing in general:
It took VERY long to balance the things as they are now. Hundrets of humen games and human vs AI games where played and tons of simpulations were made AI vs AI.
I don't say its perfect, but I already spend a LOT of time to balance it and I am really someone who plays MG like mad. So please first play it a bit longer before you decide that something must be improved. For example persian and magic are often played bad by humans ( AI plays magic bad too
). But if you are really good and you know how to use archmages without smashing all of your own units, you will wonder how strong magic is!
What do we have:
We have factions which are DIFFERENT and I like this fact! And my target was not to have completly equal factions! with just another look.
After a while I also started to love the fact that the factions don't all have the same strength because this allows a lot more fun setups.
It was not the target to create a 1on1 e-sport game! The target was to create a good balanced techtree which allows tons of fun setups ( which are not completly unfair ).
And especially coop game setup was what I had in mind ( and games vs AI in general ) and these can really be setup in many fun ways now!
If you really want to play 1 on 1 you can still choose the same faction. But typically players are not equal. There are good and bad ones. If you now setup a game you better choose something thats fun for both. (The good player uses for exampe magic , the bad one chooses norsemen or Romans.)
Some small changes are ok( like some of the things claymore mentioned a while ago) but in no way huge changes which change everything.
If you want this, just copy the megapack and modify it or make your own mod. It's all open source :-D .