As you advance in the game, you find that the population of Nations is not evenly distributed. This makes it more difficult to acquire certain types of National Trade Goods. Here's a suggestion for a new building, the Trading Post, where one can exchange their goods. The exchange rate should be costly, like 4:1 or 5:1. And usage should also be limited in some way, perhaps require a worker and some clock time to complete a trade. And upgrading the building could reduce the clock time for a trade? But for those cases when you really need one more Tea, it would be great to have this option.