I always thought the problem was not that the AI was being intelligent by creating alliances and violating them a turn later, but that they were violating the rule-set of the game. I could not find any way for the player to cancel alliances. That and alliance features working, namely your allies declaring war on aggressors.
It's perfectly possible that I simply couldn't find how to disable alliances, but that raises a potential interface design issue.
Here are two more things that I hope will be fixed in the new diplomacy build:
 I'm sick & tired of the wildly irrational value that the AI factions put on some trade items. It has no basis in reality. To make matters worse, if you do cave in to their outragious demands, the game intentionally tries to humiliate you by asking "Is there anything else you want to give me?"
Come on guys, why are you intentionally trying to discourage diplomacy? My suggestion would be to either fix these things or take most of the diplomacy out of the game. You can't have it both ways!
I would consider that a feature really. They are after all extorting you.
Misread, but with the exception of trading influence I don't recall it being that bad. I think it's a little too easy to con everyone into declaring war with each other when you are in a winning position.
The post-deal dialogue is effected by their present relationship with you as well right? Did you have negative relations with the faction?
The only suggestion I would have for Sovereign diplomacy dialogue is more textual flavor to highlight individual Sovereign personalities. This way Procipinee may be coldly cordial while Verga is above illustrated douche.
If this is ever pursued, I am hoping that this is something that can be modified on Sovereign creation and isn't associated with faction.