Part of the Enhanced Estates feature that was being worked on, but which has taken a bit of a back seat to a complete estate overhaul, was similar to this. Each estate would get a certain number of "plots" on which the estate owner could build various things. The bigger the estate, the more buildings. Buildings would do different things. You could build a sawmill to paid wood production, a family chapel to support your religion, a "family museum" to boost your prestige, plus several other cool things. This could be integrated into New Economy goods, as well, with knights getting a share of the regional goods production as well as direct gold payments. The knights could then sell off these goods to make more gold, at whatever prices they could get.
The buildings would become permanent parts of the estate. The lord could assign a new knight to an already established, but vacant, estate.
This is still on the back burner. It wouldn't be done until after the current estate overhaul is done. Progress is moving on that, but a bit slow. Tom is working on redesigning some of the back-end system in order to make the programming system more consistent, and less prone to bugs and inconsistencies.
