I don't see why Origin Private File System needs some fully virtualized nonsense. You can just create some fuck off far out directory for the site for this cause. Should be fine.

There's already pretty safe secure & altogether sensible options for giving websites access to files. Alas it's all via even slower even worse abominations that File Access Handles, because spec authors swear it would be hell on earth if they didn't quintuple buffer every read or write, will swear we could never ever trust devs to ever possibly do a good thing. There's been such a constant hedging that being slow & adding layers of safety to io is necessary and it's taken literally decades to get even these crap ass concessions. I know this is impolite and I'm sorry but what cowardice, what unrelenting sad clutching of pearls. What utter betrayal of Extensibile Web Manifesto. https://github.com/extensibleweb/manifesto