I don't agree with the OP's idea but I'm not averse to a more nuanced and guided AI empire generation than the current system where the computer seemingly just picks random things out of a hat and throws them at the wall.
There is a joke in russian game development.
"Do you know how russian game developer doing procedural generation? He will write a big, thorough, nice generation algorithm. On assembler. Then he will try to put it into game, system will grant a great deal of paradox results, so he will spit and just put random. As his stories about cool generator will be in Net, fans will try to decypher it's logic."
If anything the AI should start with a personality and work backwards from there, instead of just shotgunning a wall and seeing what picture fits the dots the closest.
By the way, it's intresting issue with empire ethics changing in-game (and I'd like to know can your empire ethic change uncontrollable). How should it affect personality? If this feature would be locked for player use only, it would be boring.
Also it's a question (maybe answered) - will traits actualy weight to ethic divergence and faction appeal?