how about this as a compromise?
in civ 3, so memory serves colonies could be built by workers why not reintroduce it?
so city boundaries stay in effect as they are but if a resource lies outside one you can send a worker there to farm/mine/whatever that needs to be done there and it eitehyr goes into a pool or city.
Gangor, referring to another thread about supplies if we did use supplies why dont we tie it into city growth as an option? so a city that uou dedicate x supplies per turn will then draw those supplies from your supply pool and the city generates an extra person either to work the tiles or be a specialist.
that way supplies could be used for war/trading and growth during peacetime, essentially another form of capital that will rise/fall with value depending on the circumstances in the world essentially making a global economy in the game