I see this as possibly workable. Perhaps this could also be applied to the other Consolidated City Counties too? But I haven’t thought through the implications of that.
I agree that this would be an improvement on the current tagging.
I also think that more mappers would expect, and more data consumers might produce better results with, San Francisco present as an admin_level=8 boundary than without it. That’s not the be-all end-all argument to be sure, but I think it’s a strong one. But these places are always going to be edge cases, so there’s never going to be a perfect way to represent them.
As an aside, I appreciate the discussion and how you and all the participants have been trying to work together to find a workable solution.