What would you change in Heroes of Might and Magic IV?

The only thing that needs to be fixed, or rather improved, is the AI. The AI's behavior during battles is still acceptable, but on the map... I won't give examples; I think everyone knows and has encountered the AI's blatant stupidity in Heroes 4. The strangest thing is that it's completely different in other versions (3.5). The logical question is: what is so unique about the mechanics of Heroes 4 that prevents the AI from being properly configured? Also, improving the lower-level units is a great idea! So that levels 1-2 are not practically useless, but are as in-demand as levels 3 and 4.