WHY MOD ?

[Uh-Nu-Buh]

So, you are asking for a Mod that makes the game harder with some units that are tailored to make up for the weaknesses of the AI? E.g. AI is weak in research, so make it's units study harder; AI fails to use/research X spell, so make it a national spell/cost less to cast; AI never uses X magic item, so give one of it's commanders X from the start?

Not a bad idea. However, I suggest you just play some humans instead! Creativity wins over brute force every time; and I would rather be surprised by ingenuity/genius than crushed by foreseen but indomitable might.