This mod is amazing to let citizens build what they want. I set a zone to everything but industry. The area doesn't increase in density from low to high residential. I'm sure the same thing happens with commercial moving to high density. An area with industry and office probably will have a similar issue. Fixing this probably requires a simulation overhaul. Buildings have to be abandoned or destroyed by hand to get replaced. In Vanilla, this is done by rezoning. How could this get fixed in the future?