The more I think of it, the more convinced I am it's Venice.
Arguments:
Venice will allow for a UU for a unit that still isn't covered by UU's. The galleas. It would be perfected at protecting the new sea trade routes, and perfectly fit that theme.
Their UB will produce this new luxury ressource Venetian Glass, that only Venice will be able to produce, and you can make one new per city you have with this building. Can be quite powerfull if you have nations to trade with.
Their UA could be focused arround the new trade system. There you go, the perfect trading empire.
Venice was on its most powerfull in the renaissance era, and this XP will focus on the ages from the renaissance and to the endgame.
If Dennis had mentioned Venetian Glass, don't you think we would have guessed on Venice? Buffalo can be most NA tribes...... and you will have the problem that other civs can get the ressource if it isnt produced in a city by a building.