Right, that came up the last time sshfs on the Kindle's side came up: it needs an ssh client in $PATH, one that's actually called ssh. USBNet only install the dropbear client as dbclient, IIRC. No idea if it would handle dropbear's client, or if it actually requires OpenSSH...
Either way, I have an OpenSSH build on hand, since I build the server, so that's not terribly annoying.
One other thing: since part of FUSE actually lives in the kernel, I'm not quite sure bundling a newer fuse userland library and/or one built against a different Kernel is completely safe. If it blows up, that's probably why ;p. Not that familiar with the FUSE API/ABI, so the point may be moot.
Probably can't get around the fingerprinting, that's SSH after all
. It'll probably need an SSH client that stores/expects a known_hosts file in a directory that doesn't go poof after a reboot, though.