You'd think so, but we actually already have such a thing, and it's not doing anything to mitigate the issue it was designed to address.
A city ordnance was passed in the late 70s, IIRC, which says that for every SRO (Single-Room Occupancy, basically, long-term flop house) in the Tenderloin that a developer wants to tear down and replace with a high-rise hotel or whatever, that developer must also put up another building with an equivalent number of SRO units to the one being torn down, somewhere else within the 7x7. So, you have to build two buildings for the price of ... well, at least two.
Now, given the current rental market in SF, I can't imagine we're actually very far from (or even already over) the inflection point where that becomes economically viable, but it's demonstrably not affecting the new construction rate in any way I've noticed...
A city ordnance was passed in the late 70s, IIRC, which says that for every SRO (Single-Room Occupancy, basically, long-term flop house) in the Tenderloin that a developer wants to tear down and replace with a high-rise hotel or whatever, that developer must also put up another building with an equivalent number of SRO units to the one being torn down, somewhere else within the 7x7. So, you have to build two buildings for the price of ... well, at least two.
Now, given the current rental market in SF, I can't imagine we're actually very far from (or even already over) the inflection point where that becomes economically viable, but it's demonstrably not affecting the new construction rate in any way I've noticed...