This wouldn't be necessary if we weren't using zoning to restrict supply. The restrictions are what cause scarcity, and it's the scarcity that drives up prices. Land owners are already well incentivized not to let housing sit empty, unless their housing's value is being artificially pushed upward through the scarcity we create.

Basically, if we quit creating the housing problem with zoning restrictions, you wouldn't see housing sit empty, and it wouldn't matter anyway because the motivated self-interest of FAR more people would build housing to meet demand.