I think that you're over complicating things a bit... Quite simply FTP access is a requirement if you're the one being tasked by the owner to upgrade, modify, or backup the UBB forums.
There are no special privileges really required, FTP access would be full access to the web space that the forum is hosted under.
I believe that if the organization has tasked you with the maintenance (upgrades, modifications, etc) of the forum then you need to have access at bare minimum to be able to modify the forum files...
