There are a few fundamental problems with your idea.
First and foremost, real world demand for resources such as banks, grocery stores and the like is generated based on where people live and work, and the routes in between. In real life, the busy places are those which sit near or on a nexus of these routes and locations. Because only so many people can be fit into a single area, the distribution is largely even, and where it's not competing business will naturally split things up.
In order for the same to be true in most MMOs there would have to be radical changes to very nature of how people travel and live. As it stands, in WoW players bind themselves to a particular Inn and this becomes their home. There is effectively only one inn per faction per neutral city, so all players of a given faction are filtering through the same home. Thus, it doesn't matter how many alternative bank or other resources you spawn, as long as all players enter the city through the same home it doesn't change which resource is closest to home. This resource will always be the busiest no matter how bad it gets.
In order to avoid this you'll have to spawn additional Inns, but this presents its own problems. Players will filter on their own to new Inns, but this requires they're aware of them and willing to put up with relearning where the local resources are positioned. Moreover, the population can quickly expand again, requiring a new inn and players to once again move and relearn their bearings. This continual displacement is neither fun nor productive.
Another issue are the unique locations that can't be duplicated without stretching disbelief. A memorial for an important lore character, the citadel containing the leader of the city, an important dungeon or lore location, all of these things can not be duplicated. Thus, you have to provide a method for players to instantly transport themselves to these vital locations in the city or face the natural inclination of players to plant roots nearest to these important places. The game can keep spawning new inns and resources to its heart's content, but players will avoid the outermost edges like the plague if it increases their travel time these pivotal points.
It's not an impossible problem to solve, and an MMO implementing something along the lines of your suggestion could be interesting, but it isn't a complete solution as it stands.