I'm generally in agreement with avoiding "one trick AI" stuff like filling the map with AI Eyes and prefer things that change how the game plays in a more interesting way, but some of the AI types that have made for particularly "interesting" games for me don't really have anything special about them other than the units they get. There's a little variety in terms of wave multipliers and things like that, but ignoring that, playing against something like a Spireling compared to Vanilla is a very different experience, purely because of the ships they use against you.
The dramatically different feel of how the game plays in that case comes entirely from how the existing AI mechanics act differently depending on what resources the AI happens to have at its disposal, not because of additional AI mechanics. With well thought out starting conditions (units/structures available, wave modifiers, etc.), you can actually get a decent amount of variety in results even with the same ruleset of AI behaviors (although adding extra behaviors along with that increases variety even more, of course).