If you buy an empty lot as an investment, and then the city grows and you want to sell that lot so that a developer can build a high-rise, you want to stop them? I mean unless you want to ban ownership of land then you are in a tricky resource. What if someone builds a lean-to in your hedge?

If anything, maybe we need to zone areas for improvised housing. Would make it easier to police for violence and to provide access to community resources.