There was some discussion in threads awhile ago about a "diplomatic" trait that would improve a civ's ability to negotiate deals in diplomacy, conduct treaties, improve The UN would trigger a GA for this attribute, and perhaps embassies would be free or something.
As for agriculture, bringing it in to use for the Mayans would be a great excuse to actually have the Mayans, or the Incas for that matter.
Has anybody given any thought to a system of negative attributes? One of the few innovations of Tropico was to force you to pick a flaw as president (e.g. flatulence, drunkenness, etc.)
E.g. China "orthodox" - new techs take a turn to take effect
"rebellious" for France and Russia: random city collapses into disorder now and again, and anarchy lasts longer.
???