It sounds like git-annex to me (doesn’t have to be 3rd party hosts, you can combine your own systems) where it allows decentralized file management across all your devices. I’d also be curious to see how they handle offline backup/file tracking and the sneakernet use cases (something git-annex supports). As it sounds like it is a true filesystem, it could be a nice upgrade assuming feature parity (one gotcha with git-annex, is since it is using git, you can’t easily have other git repositories inside of it).