Is there a way to setup a single "master" ftp account that will allow someone to login, and then process multiple sites?

Rather than:

Domain1 user1
Domain2 user2
Domain3 user3

To just allow user1 FTP access to all 3?

Server is running Plesk 7.5, on Fedora.

Client has 300+ domains and wants to use a single FTP account to manage them all.