My question is how will these buildings be available? It does not make sense to build certain buildings in certain areas. No point in building a mine in a rural area.
Many of the buildings that I would consider building could be tied very nicely into resourses. Mines, grain mills, lumber mills. If we really expand resources-vinyards, orchards, brewers. Will someone have to decide what bulidings can be built in each location?
On a second note, how would the buildings be tied to the estate? What happens if the estate is removed? Do the buildings get destroyed? Can a lord move buildings from empty estates into occupied ones? This would not so much be moving the building as much as changing the boundaries of the estate. I could see being able to move a building from a knights estate as well, but make sure knights can protest those actions.