[I retract this comment entirely, apart from the pleasantries and the preference of being wrong—see downthread where rewq4321 corrects me.]Heh, didn’t notice the username match there!
I don’t think “rough edges” is the right characterisation. What OPFS provides is just nothing in the direction required. The kind of file system you need to build a database on is a fundamentally completely different beast, with only unimportant surface-level similarities. It would generally require a complete replacement of the backend, with quite possibly literally no code in common.
I’d like something like this, because it’s certainly genuinely useful for cases like this, but I’d honestly be surprised if it ever happens, because it’s just… not webby. To be useful, it just about requires that the whole thing be backed by an actual file system and exposing that, which is something that has been assiduously avoided so far in the design, probably in significant part because it discloses quite a lot about the host system (fingerprinting; disk performance characteristics, quite possibly even file system identification by various nuances in behaviour; and surprisingly large side-channel attack possibilities, mildly similar to the fuss over high-resolution timers), but also because it tends to be a security hazard, just another moving part where things can go wrong more easily than you imagine.
I strongly suspect it will end up a bit like Web SQL: a nice idea that pretty much everyone agrees is a nice idea, but which is also a non-starter for other reasons.
But I wouldn’t mind being wrong. I do want to be able to deploy a robust, high-performing SQLite in the browser.