If some nation likes you and treats you good and you betray them, do you think that they would stay trusting? And, there is no such thing as a sucker all of the time, just as trust is something that is earned.
Of course they wouldn't stay trusting. But the damage would be done, and you could have an insurmountable lead by that point. My point is that a smart AI would be nice to you only to the point that it's convenient, and it would
expect you to backstab them. Why? Because the game is about WINNING -- and if the other guy is dead, then he can't win. He expects the player -- as most players are -- to be a jerk. And in anticipating your jerkness, the AI would try to backstab you first. And even if you weren't planning on backstabbing the AI, the AI gets a smart advantage by backstabbing you anyway.
That's the personality that pure competition competition breeds.
I do want a greater variety of personalities in the AI, though... but the point I'm getting at is that it's not as simple as creating the AI personalities. If I were playing against a number of human personalities -- one a King, one a general, a economist, one a doctor, one a lawyer, one a bartender -- I would be the most ruthless general. I would kill the King, kill the economist, kill the doctor, and kill the lawyer. I would do it one by one, smiling at the rest of my so-called allies while I conquered my latest foe. Once I had a huge lead, I would easily kill the other general too. And then I'd win.
If you want to add new personalities to the game, the key is making it profitable for the HUMANS to play with any kind of personality. Then the AI will fall into place:
How will I profit from taking a city from the greatest King if my new subjects refuse to acknowledge my leadership, and make it nearly impossible to govern them?
How will I profit from attacking the greatest economist if every other nation's trade depends on them, and suddenly I find everyone allied against me?
How will I profit from backstabbing the greatest lawyer, if it sets a horrible example for my citizens at home -- that you can break a deal whenever you feel like it?
How will I be able to successfully attack the greatest bartender, if he keeps all my citizens drunk?
My point is for personalities to be a good addition to the game, you'd have to make those personalities
profitable. For example, an awesome economy with a decent army would need to be as effective as my decent economy with an awesome army.
The problem, right now, is that an awesome army beats everything. It's the highest trump card. Not to mention that an awesome army is best used in the most dastardly way possible. One ideal strategy, one ideal personality.