Reading another thread about moving food I thought of a way to do this it requires more coding (mostly for the graphics, and AI use) than I know right now but should be to hard:

New Resource:
food shipment 1
food shipment 2
food shipment 3

New National Wonders:
Food shipper 1, creates good food shipment 1, minus 4 food to city creating
Food shipper 2, creates good food shipment 2, minus 4 food to city creating
Food shipper 3, creates good food shipment 3, minus 4 food to city creating

Food Receiver 1, + 4 food -1 commerce, must have built Food shipper 1
Food Receiver 2, + 4 food -1 commerce, must have built Food shipper 2
Food Receiver 3, + 4 food -1 commerce, must have built Food shipper 3

Now if there is a way to make this not count against the max number of national wonders in a city?
And I would make these pretty cheap to build

Edit:
or you could make it a nation wonder:
Food Shipper -4 food in city
Normal building
Food receiver +2 food in the rest of your city.
But that would probably be way to powerful, as it would multiply across your empire and heck could even build it in the shipping city