I'd like to see both an automatically adjusting dynamic tax on owning more than one property in the same municipal or arbitrarily useful region, as well as dynamically banning the ownership of more than one. Everytime I mention this, I get "blah blah we have a democracy blah blah freedom" etc.. but it's no such a democracy if one particular age-range dor demographic of people owns all the assets and politically protects them from diminishing in value or facing competition. Pending presumably complex implementation details, but a healthy system that prevents generational fiefdoms would probably adjust to severely disincentivise even the possibility of acquiring more than one of the most important finite resources in urban areas.

Pied-à-Terre Taxes are pretty easy taxes to implement, because usually the ones affected may not even live in the town/state to vote against it to begin with. But ultimately this only covers a very small slice of homeowners.