I recently needed to move all my private domains to a new hosting solution and the new solution did not allow any other access than FTP. I considered setting up a mirror on my ubuntu host at home but that didn't feel like the best solution. So I thought there must be a way to mount a file system using FTP. And there is several I think. The one I tested and that looks good so far is curlftpfs. The only tweak not mentioned on the curlftpfs site (in an obvious place) is that you need to put the following in your /etc/fstab to make sure all users (and not just root) have access to the mounted file system:
curlftpfs#ftp-user:ftp-password@ftp-host /mount/point fuse rw,uid=500,user,allow_other,noauto 0 0
"allow_other" is the magic enabling all users access. Since it uses FTP under the hood you will notice the file system is quite slow at times. Especially when editing large files. But compared with having a local mirror and updating all changed files when needed I think this a pretty convenient way to access the files on the FTP server.