Suleiman parked a great diplomat next to one of my cities and hasn't moved it for over 50 turns, so that's perhaps something to look at.
I wish religion had a more tangible effect on diplomatic relations, especially in the form of positive and negative diplo modifiers. As it stands now, as far as I can see it only happens in three scenarios: 1. You spread a religion to another civ and that civ is happy about it, 2. You're spreading and the civ isn't happy and 3. A religion spreads to you and the founder is happy. I wish other scenarios had related diplo modifiers - if Civ A spreads its religion to civs B and C (both non-founders), it should be a positive diplo modifier between B and C ("majority of your cities have adopted the same religion), if civ A and civ B have founded different religions, it should be a negative diplo modifier (I've seen denouncements because of religious differences, but haven't noticed negative diplo modifiers) etc.
Also, it seems counterintuitive that when the AI asks you to stop buying land, you're better off in the first 20 turns if you told them to bugger off, since you get a permanent -30 diplo modifier, whereas if you promise to stop, you start by getting a -50, then the next turn -49 etc. In those 20 turns, that -20 modifier difference might make a difference between getting declared on/denounced and not. Furthermore, it seems odd that if you make that promise and then after 10 or 20 turns the AI declares on you, you're still bound by the promise - imho, if you get declared on by the AI, your past promises to them should cease.
Another thing regarding AI's strategy - in my current game, Ottomans are between me and Sweden, who has 12 cities compared to Suleiman's 6. Suleiman declared war on Sweden and was holding its ground very well for the first 20 turns. After that, he attacked me (nothing happened between us in those 20 turns to prompt this), and it wasn't a bribed war ("negotiate peace" button was there, and he also beforehand sailed many of his units (including land) to the other side of my empire (which was very smart tactics-wise)). Following that, he started losing badly against Sweden and has thus far lost a city. It seems odd strategy-wise first attacking the clear leader&neighbour and then so soon attack the other neighbour by sending so many units so far away from owned cities. I was also sending lots of iron and horses and other stuff to Suleiman to help his war efforts, so he lost that as well.
I'd again float the idea of being able to negotiate "non-aggression pacts" (different than defensive pacts) and "don't declare war on ____ for a certain number of turns).
Excellent version (besides the defensive pact thingy), the game is continuing to improve tremendously, so kudos to all!