You're transferring files you don't want to, that's amazing
Talking about your feature request, it's nearly impossible on download and on fxp. You need to read the file to be able to extract the genre, the year or whatever other info from the id3 tag. The ftp client can't do that ; it can only transfer files and send commands to the ftp server.
It would be possible on upload since the files are stored on a local hard drive, but I think this feature is a bit too much for a ftp client.