Do you really think the main constraint on supply comes from rent control and not zoning limitations? In SF there is a strong desire to preserve the historical character of the neighborhoods (agree or disagree as you like, but the political will is there) and I think that's the root reason why it's difficult to demolish buildings and rebuild them with more units, not the mechanics of rent control.

In any event, even in a rent controlled building, you absolutely can terminate all of your tenant's leases and kick them out, upgrade the property, condoize it, and sell the condos (Ellis Act.) The only restriction is that you must sell the units, not rent them.

(speaking as someone who, as a side project, is in fact building high density residential units in SF)