Hey Greg, glad you are putting work into trying to help the affordable housing crisis in San Francisco. However, I’m fairly certain that it is possible to change the general plan and zone through local ordinances. The California Supreme Court ruled in favor of it in the 1980’s. (Arnel Development Company v. City of Costa Mesa, 28 Cal. 3d 511 (1980)). It’s considered a legislative act and therefore can be done through the initiative process. Good luck!