the only thing wrong with the battlefield AI is the campaign AI
sending it off to war with inferior units.
Then what about:
Suicidal generals?
Units reassassing wether they should really charge 20 metres before the enemy line?
Missile units charging ahead of their friendly melee units?
Missile units starting to shoot at 2/3 range instead of full range?
Cavalry units charging enemy missile units unsupported?
Siege battles?

But it was a nice plug for your mod