This is how the download basket feature will work:
-User needs to be registered on AMP.
-User add files to the basket while surfing on AMP (with a counter somewhere on top of the page)
-Once the basket is over, a few options needs to be set to complete the process (like moving mod. to .mod in filenames, remove weird character from filenames, receive archive by email or receive a dynamic link by email to download the archive later)
-If sent by email the archive will be deleted on the fly
-If sent through a dynamic link, the archive will be removed from AMP after a few days (sometimes downloads fails you know

)
-The maximum size of an archive is 10MB, enough to store more than 50 modules.
-A cron job to process the orders (create and remove archive, send emails...) running every 10 or 15 minutes (depending on the load of the server)
Of course the max archive size is not big enough to download every musics available for some composers (like Lizardking or 4Mat).
I'm working on it...