As for merging and extra options, it can certainly be done. Also the creation of user keys. known_hosts management would require changes in the OpenSSH itself, which I'd pretty much would like to avoid. As for Unicode input - there are places to ask for help if you cannot get it to work yourself (mzone, mailing lists).
I don't see how ssh-agent would be impossible, it just wouldn't be as safe as on *nix. That doesn't really belong to the SSHCon project though. Same goes for scp/sftp - this is totally unrelated to SSHCon itself. And finally, same goes for tunneling / VPN.