We have long wanted to enhance knight's estates by allowing them to create buildings on their estates. One of the ideas to go along with it is that the buildings would have effects that could alter things in the region.
Moscow used to be divided into a bunch of districts where each was basically a city of its own, with its own theatres (because who would be so poor as to go to another noble's theatre?) and the like. Kind of sounds like what you are proposing.
