I think it's fair to say everyone wants the Old Mint preserved and turned into a Museum. The question that's causing all the consternation is who will develop and manage the museum: the current SF Museum and Historical Society, or the California Historical Society.
The former has had ten years to develop the museum and done yeoman work, but much remains to be done. The latter is the new choice of the landlord, the City of San Francisco.
I've been in the museum and exhibit biz for many years, and I know what an incredible challenge converting the Granite Lady must be. These giant historical structures suck up money like a sponge, with endless needs to make them modern code compliant. The list is staggering: earthquake standards, fire suppression systems, Americans With Disabilities Act requirements, elevators, environmental controls, OSHA standards, toxic abatement, and more. And this doesn't include installation of gallery fixtures, displays, and lighting.
Then there are the challenges of turning the interior with its maze of rooms into usable gallery spaces. Imagine the headaches of trying to display mega-artifacts such as a cable car, earthquake shack, or fire engine within these rooms. From my visit to the Old Mint, the only existing large-scale spaces seem to be the central courtyard (which would need to be roofed) and the two 'counting rooms.' And how would you get a mega-artifact into these spaces? A crane? There are no doors to these rooms from the street.
Not that these challenges can't be met, but the costs for engineering and construction will be gargantuan.