Thunderbrd
C2C War Dog
I think I have figured out how only those nations importing trade goods can also get economic benefit from them, The producer is already getting the benefit. I a thinking each trade good would have an importer of that good that can only be built in nations without the culture needed to build it.
Interesting idea, importers... available if you don't have a native source of the resource but do have the resource. That could really enhance the trade side of the game.