Add "removable media" access, and some form of copy mechanism. The idea here is to allow for someone to pop in their usb key with a load of mp3's on it, and copy it to their me music directory, without exiting me. Or simply access the music on the removable media, just as you do with cdroms.
There is a workable solution without the programmers of ME involved, and that is to simply mount your removable device as a folder somewhere in your ME database path. You can do this with the linkd utility from sysinternals.com, or through the disk management user interface in computer manager. Then, when the usb key is plugged in, and if ME's dynamic database is working, you can cd into it from within ME and play the songs on there.