The most challenging maps for you.

I need it, and many other people do too. If the AI's strength doesn't come from nowhere, but it actually plays on its own, that would be really cool.

Let's not forget that the computer doesn't follow the rules... if it's smart enough, it will use a diplomacy mod to gain a huge advantage, rush in during the second or third week, and wipe you out... or it will overwhelm you with a mage and blue sprites... so be careful what you wish for! No one thinks about the negative consequences!)
P.S. I won't even mention author-made maps, because the computer won't give you a chance there.
P.P.S. I'm not talking about the length of its turn, because the computer shouldn't take that long, as there's quick combat...