An sftp server and/or client would make it easier to work with remote filesystems over ssh.
I have an older server implementation at https://github.com/creationix/sftp-server
This needs to run inside a secure channel like ssh or node's tls stream with application-level authentication.
depends on #1
Strictly speaking, this can work independent of ssh. I used it to mount my webos tablet as a sshfs fuse filesystem in my linux desktop (with a special flag that skips the ssh tunnel). But for mainstream adoption, ssh is best.