What did I missed from Dom I.? -> DIPLOMACY!

[Mortifer]

All right I think we had nice ideas so far, maybe trading items should be restricted, I agree.

If the AI can be scripted to have long memory, than the abuse problem will be solved.
If it will 'remember' everything, what the player did, than we won't have problems.
It must be tweaked perfectly, and that will be the hardest part of it.
[How will the AI react in various situations, like getting a province as a gift, etc.]