The folly with arguments blaming San Francisco for the problem is the fact that the entire Bay area is priced at an insane level. Take another look at this [1] BART map with corresponding home prices for each stop. Yeah, it's cheaper to live outside of the city, but it's still crazy expensive. The median sale price for a house in Pittsburg is $430,000, with a 62 min commute into SF. If you live 62 minutes outside of…
But even the housing policy you describe, in which SF acts unilaterally, would still be a great good. Tens of thousands of people previously priced out of SF would now be able to live in the city. And those who still couldn't afford the city would find it much easier to live within a reasonable commute.