Every time when I uploading a new items on AJ, I catch myself thinking that the stage of marking files (manually specifying what is the main file and what is the audio preview) is unnecessary. It can be done automatically based on the file extension.
Usally is uploaded 3 files: MP3 preview, a zip archive that contains the main files and, optionally, jpeg or png thumbnail. There are no other options. Besides, as far as I understand, these files are analyzed. After all, if you specify, for example, that preview is a png file, you receive the error message.
Automating this process will save not much time, but will help to reduce the amount of routine work. I would be glad if this step can be skipped, and I hope other authors will agree with me.