You will need a lot more information and capability in order to do this. At the very least, you will need a good knowledge of systems administration of your system and its server applications.
You will also need a working development server with the same software set as production.
You will of course require root access on both the development and production machines.
Assuming all these things are available, the setup is possible in principle; there are many ways of tackling it. Personally I'd recommend storing the FTP users in a database (if supported by your ftp server software).
Mark