You can't just convert office space into residential space. Completely different building codes. Just the retrofit for the plumbing makes it untenable.
I know this will get downvoted but, I say Throw the building codes out the window. Housing people is more important than regulations.
If it made a difference to your ability to get shelter, which would you rather choose: have shelter or live in a illegal tent under a bridge resting assured with the knowledge that there's a big book of rules in place.
The problem is not all codes are meaningless regulation, and some of the important ones are indeed expensive (and vice versa). If you yolo it, you get cases like the Grenfell tower fire, and a lot of people literally die.
This is how you get housing tenements, and SF has a history of over-paying for impermanent housing solutions (like tents in a parking lot, or cots in a navigation center).
Not all buildings in SF are high-rise open-plans. If you're imagining converting Salesforce tower, I see how that would seem impractical.
Most commercial office space in SOMA (old warehouse buildings) can be converted into live/work lofts.
If you're talking low-income housing, it could be closer to a dormitory setup. Common bathrooms and kitchens, etc. This used to be common in low-income urban rental property, and still is in some parts of the world.
Building Codes are words on paper. They can be changed more easily than physical buildings.
Think of most offices. Central elevator shafts and stairs and bathrooms. A massive floorplan with all the windows on the edges. How do you convert to residential? Have 5 feet by 500 feet units so everyone has light and a connection to plumbing by the elevator shaft? Residential buildings have a lot more access to natural light throughout the structure and they are plumbed entirely differently. Hvac and wiring too.
This doesn't describe a lot of office space in San Francisco, especially SOMA. There are a couple of high-rise open plans (like SF Tower), but many offices in SOMA are converted warehouses.
Check out 510 Townsend, one of the properties mentioned in the OP. What do you think about converting buildings like 510 Townsend into live/work lofts?
The problem with shared bathrooms & kitchens is that no single person is responsible for cleaning them and as a result they end up being messes. It can work (in theory), but in practice it ends up getting ruined by lazy jerks.
Dorm buildings are still thinner and have more access to natural light. No matter what you get these awkward units and dystopian unlit spaces internally. In places like nyc with huge, city block width apartments, there are actually internal voids that let in natural light deeper into the structure.
If it made a difference to your ability to get shelter, which would you rather choose: have shelter or live in a illegal tent under a bridge resting assured with the knowledge that there's a big book of rules in place.