One thing which has always slightly irritated me about Civilisation is that while gold is collectively pooled, and that can to an extent be used to hurry production (plus with certain mods, including C2C, one can create merchants and suchlike to hurry production in other cities), it's impossible to move food from one city to another. That means one can specialise in production, or gold, but a city surrounded by highly productive mountains is never going to grow very large, even if you have a nearby city producing large surpluses of food, with little to do with the gain in population but set them as specialists. Does C2C add any way to have one city provide food to another, perhaps in the style of Master of Orion? (Essentially in that game, for those who don't know, you build 'freighters': ships which don't appear on the map, but can each transfer a set amount of food between planets per turn.)
If it doesn't, then consider this a suggestion
EDIT: Oops, somehow I typed 'are' instead of 'any' in the title. Sorry about that, not sure how it happened 
If it doesn't, then consider this a suggestion

