That's an interesting philosophical point. There are definite future use cases for working with distributed or network-based file systems.

But the issue I needed to solve first has always been the one dealing with the purely local aspects of the system. People need to be convinced that this local system is as rock solid as all of the local native systems they're always working with.

The issue is that's not under your control: browsers can and will delete the data. https://gist.github.com/pesterhazy/4de96193af89a6dd5ce682ce2... covers the issues related to indexeddb, and I wouldn't be surprised that similar limitations exist OPFS. Practically, either you have internet, and so storing data elsewhere is more robust (and treating any browser-based storage as a cache), or you don't, and running a "native" app is simpler than trying to run a PWA in the offline browser (and storing the data on the local file system means users can actually access the files outside your system, vs whatever opaque setup the browsers have).

That's not to say your system isn't interesting, it's that it's likely going to hit many of the same issues as previous approaches in this area (e.g. https://offlinefirst.org), and so you need to work out how to solve those issues.