What is the best way to balance out the combat against the AI in battles (campaign)?

[Rahwana]

add some big economy bonus manually in EDB, and made the unit recruitment 0-turns, the AI will spam fullstacks after fullstacks, don't believe it? Play Roma Surrectum 2.

Huge economy bonus (NOT SCRIPTED ONE) will push the AI to recruit more, and actually, they will recruit somultaneously with 0 turns recruitments, when they have their money. So... you'll get big battles after battles, and most often you'll play your 2 stack vs 3 AI stack, that will even the playing field more since your another army will have suicidal generals as well, and you must do the best job to keep your "ally" alive

But when you are not a big fan of battles after battles, you'll found that boring