Simple AI rules eh?
Well I'm sure there are others who are better equiped to deal with specifics, but I'll spew some thoughts out just in the hopes to get the ball rolling.
It seems to me that perhaps the AIs are not focused enough, maybe they have too many inputs to weigh and consider, and those inputs are not yet balanced correctly, or perhaps even fataly flawed due to slight game mechanic tweeks (such as dealing with supply better, and worse).
With that in mind I'd like to see a set of AI styles that focus the AI in one (or maybe a few) direction for the entire game.
Examples of these styles can be picked up from other TBS games, AoW1 and MoM had settings for the AI to follow (expander, conquerer, defender, ...) so perhaps it is posible to give these styles to the different AI nations in a game, and let them try to focus their energy in specific directions (it would be interesting to let the player even pick the style, or leave it as random). If it is randomized each nation should probably have weighted choices as certain styles will better fit certain nations.
Ok so now we have a rough framework from which to work with. Lets try some specifics.
Firstly the style has to be picked (or incorperated) from the instant the AI designs the nation. Lets make two broad styles with several sub-styles possible within them. The two broad catagories can be Might and Magic (
). A nation with a Might style would focus on creating armies based on strong recruited units (not militia and LI) a nation with a Magic style would focus on creating armies with mages and or summons, not relying as much on the stronger (more costly) recruitable units. Obviously there would be some overlap between the styles.
Sub-Styles could be things like, expander, conquerer, defender, builder (economizer?), researcher, ...
An expander would attempt to expand its boarders through indies, trying to avoid early national conflicts, a conquerer would expand by starteing early national conflicts, a defender would expand, and try to build up more internal defense before attacking new provinces, a builder would be similar to a defender I guess or you could make it an artificier, a researcher would devote more resources to mages and getting spell levels quickly. Furter distinctions within these sub-styles could be based on how many resources are spent on buffing commanders vs. summoning vs. more units.
The main idea is to give each AI a path for it to follow, rather than allowing it to dabble a little in everything (which is rarely going to make it successful). This doesn't go into strategic elements for actual game play, but others can work on those issues better than I can. One thing that the AI needs is the ability to use powerful combos. In fact the styles can be made such that they aim toward these powerful combos.