Much as I like the idea being able to tweak Civ 4, and that it will happen it is probably to soon right now to say anything.
One: we do not know how smart the AI is. First thing people should make an analysis on whats actually in place and what could use improvement
Two: We do not know the extend of support for AI development. Its all based on speculation right now and until 2 days ago people did not even know what the city screen looked like, let alone the architecture of AI plugins.
In short: good idea, but we need more info prior to us making any further plans. I believe Firaxis said they will first release the game and follow it with the SDK so it might still be 1 or 2 months before people can actually get started on AI mods.