A couple realistic policies are:
First and foremost is addressing the affordability crisis. Roll back zoning regulations. Allow smaller housing spaces, reduce building costs, and streamline the building approval process.
Crack down on drug dealing and theft. These issues perpetuate and feed into the homelessness problem.
A less realistic possibility that would be dead on arrival is converting some of the copious green spaces in SF into low income housing units. Converting half of the presidio of GG park to SROs and RV camping would drastically improve the stable housing options for homeless.