Filesystem in Userspace is supported on pretty much everything, but the support and requirements vary to set it up. SSHFS does this. See fuser crate for modern Rust libary.
For MacOS, we'd actually want the Finder Sync Extension, which is what I believe MountainDuck uses to provide a fantastic experience integrated with Finder.
This would be a neat long-term feature to support a user-level file system similar to SSHFS.