The biggest constraint would seem to be political or specifically lack of willingness to update building codes in one of the largest cities by area in ca -SJ. Land is so very underutilized in San Jose. Its development on the surface looks more like an agglomeration of suburbs rather than a city proper. If they allowed for new code to allow density in the city of San Jose alone, it would go a good way to alleviating the housing shortage.

SJ is over 3x the surface area of SF but has barely 20% more residents in that area. Imagine if they just doubled density --you'd allow for the absorption of an extra million residents. If they only upped the density by 50% they'd allow for over an extra 500,000 residents --that would alleviate the issue by itself.

There is so much poorly built stock from the 60s and 70s that it would not only renew the city but it would become the undisputed powerhouse of the bay area.