Diplomacy

I not much of a programmer so I dont know how hard this will be to implement but I have always noticed my options for diplomacy are rather restricted. For instance during wars when negotiating peace only one side is allowed to give stuff, which is rather unrealistic since peace settlements rarely consist of just one side giving stuff to the other. I think have everything open to trade when negotiating peace would be better, kind of like some cut throat price negotiations.

Same thing for trading certain items, buy offering or requesting that item a lot of other things are no longer up for trade. Take for example city Alpha, I would like to be able to ask for it and in return give nation A iron and some gold rather than just asking for/demanding it.

I have also noticed that one nation will invariably research feudal aristocracy first and then five or six nations will instantly vassalize themselves to that nation. A particularly jarring example had been when every single nation I traded with vassaled themselves under Russia, my warlike neighbor. My usual tactic in such a case is to blitz and raze the offending nation, but declaring war on Cathrine in that game would have destroyed my economy. There as to be an error or something somewhere in there, half the world should not suddenly place themselves under the boot of one nation the second the chance becomes available.(I play on the upper difficulties when this happens so I am not sure if it takes place on the lower difficulties)

An enjoyable feature that might make negations more easy and put something else on the board to batter with is the idea of non-military alliances/pacts. Maybe a Trade Pact that boost the economy of both nations but should the trade pact be broken due to war both nations get a economic backlash. Maybe a one way version of the trade pact could also exist boosting the nation of one economy for x number of terms, it would be useful tool for negating peace.

Yep, there are lots of things that could be done better. Actually, I think diplomacy is the worst part of this otherwise great mod.

Vassaling other civilizations is indeed too easy, and often the one civ that has the most vassals skyrockets in points and eventually wins the game. Other thing that I really don't like in diplomacy is AI:s tendency to declare war on you just (10 turns) after you have overpowered and forced him/her to peace, not remembering how the last war ended. I like aggressive and sometimes backstabbing AI, but civs with much smaller armies than yours should not be so war-going. Of course, battling much smaller civs isn't that bad for your empire but I find it annoying that I have to force somebody to peace every 10 turns or completely destroy him.

Some of your ideas were pretty nice and could add some depth to the current diplomacy system. One addition that comes to my mind is a form of open borders that didn't allow passage of military units but would be little bit easier to get.

However, modifying these things is propably quite difficult and timetaking, and developers have limited time, so I'm not expecting much to happen in the near future.

Agreed.
I'd like the option to exclude techs like the AIs get to do. Have it redded out saying "We don't want to start trading this tech yet".
I'd like to be able to set a minimum threshold of gold for a tech. So for example, I won't receive offers for 80 gold for a tech that took me 200 RP to get, because I set the minimum gold offer to 100 or 150 gold. I don't mind selling it, but at least give me a reasonable amount for it. Something close to the RP cost.