Not sure if this is possible or not, really need to speak with Magix about it...
I think the best thing to do would be to allow users to only upload to a certain directory. Then once the files uploaded are deemed to be ok they could be moved to the appropriate place by certain FTP moderators (whoever Magix decides this should be).
I guess it would have to work something like this. Let say for example there is a folder called "Uploads" and then "Memberx" would like to upload some files. "Memberx" would send a PM to the FTP moderators and they would create a directory "\Uploads\Memberx" and then he/she uploads the files.
This would definitely help in logging who has uploaded what and stopping mysterious copyright content appearing. What do you guys think? Any suggestions?