I see. I had always assumed that the FTP and SCP/SFTP logins were restricted in the same way. They are, in fact, completely independent.
I'll do a bit of background reading, and maybe raise a FR (which, as you say, looks like it could be a lot of work, so best gauge the level of interest first).
I could see some of those other shells be very handy for secure file transfer, backups etc. The only shell I can see in the selection box at the moment is /bin/bash
At the moment we are stuck between a rock and a hard place wrt file transfer into the server. We either provide a secure means of file transfer, but we cannot restrict the landing directory that the files go to, or we provide a much less secure means of transfer (FTP) for which there are already dire warnings in the admin screens warning you not to enable it, but at lesat we then get to chose where files go, and can restrict access to that directory.
-- JJ