Responding to Steve Clark's questions about how it would affect the current "bargaining table" concept, I think it could work like this (But, like you say, it won't because Firaxis has already scrapped this one):
the bargaining table is for large/politically motivated trade agreements between countries they consist of the strategic and luxury resources.
A second trading tier below that would be a non-player controlled unit (think of it like a business class) that traded the bonus resources (wine, wheat, cattle, bananas, mangos, whatever). They move around by themselves on auto-pilot and bring you gold from their sales (conceptualize it as a tax on their trade).
The advantage would be that you gain more wealth (gold in the game) through this, but also that you can prey on your opponents caravans, or whatever, and get $$.
This would also create a commercial reason for wars and provide a purpose for having a navy (maintaining a trade empire, keeping the sea lanes open) other than "I need to transport tanks across this blue stuff because I want to knock off a neighbor"
I can think of alot of good additions to this idea: you can increase/decrease the amount of taxes on imports/exports, over time you brand of "wine" becomes the quality brand so you are paid more for it (like comparative advantage).
Will they do it, the eight ball says "definitely not". But, I think it's an interesting concept and certainly one that could be done and integrated into the game.