You cant change the AIs actions. But you can mod to the pros/cons of it.
Actually there are a number of AI mods. They remove units the AIs overuse. Or some modded nations which are specifically designed to be better AI opponents by being built around what the AI does well or doesnt do well.
There are also recommended game settings which can vastly improve AI performance
And maps have been created which can make AIs play better.
A lot of people actually play solo. Someone needs to do a webpage or sticky thread on the subject.
Here is iirc one of the more complete threads on the subject.
House Rules Against AI (improving the AI)
http://forum.shrapnelgames.com/showthread.php?t=44783