[01HNNWZ0MV43FF]

You could do a loopback network filesystem and make any user-space FS you want. That's what WSL does, and there's a Rust crate for it. Can't recall the name at all.

[Ericson2314]

There is NFS and FUSE so you can write your own implementation, but you are still stuck with the interface that the kernel understands.