I experimented with similar ideas 11 years ago with the OpenStack counterpart of S3, and basically an object storage is not a real filesystem. You can get away with a FTP/SFTP interface (for example), but that's it. Everybody wants a cheap object storage, but not the fact that what you deal with is "objects".

I wrote a NBD server to proxy to OpenStack Object Storage: https://github.com/reidrac/swift-nbd-server -- and it was fun, but not that useful.