For better security I suggest moving from FTP to SFTP (FTP via Panel->End user)
You could still use SFTP without key pairing. Have it on server end only, and authenticate the client with password instead. This is how Cloudways does it.
SFTP will require your end-users to generate SSH keys and put those keys on your server.
We're not planning on actually adding that.
However, we are planning on adding FTPS: