I read an article a few years ago about how some luxury London flats were sold indirectly - you purchased a company (which did nothing) and gained all their assets (which consisted of only one flat). You didn’t own the flat, you owned a shell company which owned it; it’s the same problem as having the wealthy create companies to avoid income tax. I think massive taxation for extra property ownership is a great idea, but I have no idea how you make it work.