It looks like the mod has no effect on AI's willingness to designate heir. May have something to do with in vanilla the AI is unlikely ever can reach absolute crown authority. It would be more fun if the players aren't effectively monopolize heir designation. I suggest adding custom AI logic and weight to choose a good heir.

This mod is meant as a quality of life change for the player. The scope of this mod does not target AI at all. I'm very sorry, but you should try to find another mod that improves the AI to accomplish your suggestion.