Rural to urban land ratio

I felt pretty good about how I posted this idea last night, which was an apparently bad night for posting, since the forums had to be restored and I lost my post, but let's see if I can recreate it with any justice.

Basically, I'm concerned about how all structures, including resource collectors, are squeezed into what should be the urban area of cities. This leads to maps where eventually you'll see more land inside of walls than out, where walls seems to define narrow corridors of wilderness rather than vital city centers, which makes little sense and is (to me) aesthetically unpleasing. My idea for creating a more believable rural to urban land ratio without messing too badly with the game interface as it is is as follows:

Food: Instead of gathering the majority of the food a kingdom/empire needs from a very small number of dense food resource tiles, have each restored land tile that spreads from a city automatically become some kind of rural area. This could be farmland from grasslands, hunting grounds and/or orchards from forests, and so on as appropriate for each terrain type. The yield of each individual tile would be relatively low (especially for harsher terrain types, like deserts and mountains, though perhaps some hunting can still be done there), but could be increased through the collection of food resources (wheat would increase farm yield, etc.), researching civilization techs for each means of food gathering (farming, hunting, etc.), or casting spells.

Wood: Building a lumber mill in a city increases the wood yield of each forest tile in that city's rural area. Alternatively, restored forest tiles would each produce a small amount of lumber, and a new lumber resource could be added on top of which a lumber mill could be built as with other resources, below.

Other resources: I don't think it would be that great a stretch to be able to tell a city to road to and harvest a resource tile, much as they can already road to eachother, as long as the resource is relatively close and the research requirements have been met.

I'd very much like to see something along these lines implemented, as it will lead to a more interesting and believable map and better looking cities, and as it will add possibilities regarding sieges and raiding parties.