@redrum I don't expect the AI to ever understand that "charge" special attack is good against infantry. I'm not even asking the AI to play reasonably well on such complex maps. What I want is to manually adjust for this blindness of the AI by forcing it to purchase more than a single type of unit, preferably a diverse unit composition. This won't make the AI much better, but it will at least make it less boring and less vulnerable to trivial counterstrategies.
I don't fully understand the AI purchase logic, but it seems like it buys units for specific purposes: sea, fodder, defense, etc. A map specifically configured mix of units for each purchase purpose would do it for me. Something like "buy 40% walls and 60% archers for defense". Not asking for the ability of the AI to assess the value of each unit in any way. (Yes, I want the AI to blindly believe that the units are balanced, and that there are no obviously op/useless units. It's the responsibility of the map maker if they are not balanced and the configured AI is suboptimal as a consequence.)
(For reference, I'm talking primarily about Large Middle Earth, and partly about the upcoming Fallen Empire.)