Hi,
often, you end up designing units for you own factions that may have fairly specialised purposes. Of course, the AI wont know these purposes, and accordingly wont use this units under remotely correct circumstances (like, building a certain unit type only in certain initiative boosted fortresses).
I would thus ask for a way to have "buildable by the AI" option when designing units. Ideally, one could also add a "favored by the AI" design options for units the AI cant really foul up much.
Cheers,
Mightypeon