Thanks for all the feedback, only time to address a few specific but every comment is appreciated.
I was wrong about having Diplomats join cities, I meant that certain buildings either gave a diplomat specialist or allowed you to to turn citizens into diplomats. My mistake.
I also thought the GP specialists increased the likelihood of getting that same kind of specialist in that city and produced GP points. If so, then a joined Great Diplomat would give points and increase likelihood of another GD, but if not, then not. They should function like othe great people for blanance' sake.
Maybe instead of Leif Erickson I'd look at giving a civ like the Aztecs another leader: Perhaps a financial leader with diplomacy/spy savvy so there is another way to play Aztecs would be fun if an appropriate historical choice is out there.
I must confess, even if Firaxis does not make another Xpack I'm hoping to learn how to mod well enough to make some of these things happen on their own. Still, I think threads like this hopefully convince Firaxis there is a market for a thought-out Xpack and hopefully they don't let the franchise just sit for 4 years before Civ V comes out.
Oh, and I like the thought of diplomats with writing, and spies with alphabet. Thanks.
I think if you repeatedly refused a treaty there should be some kind of war weariness penalty, obviously more or less depending on your civics. I think if you're beating someone down and they're pleading for you to stop, your citizens ire should be roused. Of course if they're assasinated before reaching your capital then you don't have to worry, do you?