I think this is not so much a good idea as it look first.
The tast in music are really differents, your add-on's size
will be increased by 3mo*N songs and last considering that
a few people still hear apollo "hey look that windows" radio sound
since years because they don't know that they can tune the radio
or add sound I bet many of them will cry in the forum that their m3u
list don't work anymore.
In brief I would personnaly get bored to download 15mo when
you add-on make 1mo just to discover that the guy love the rap
or hard core metal
Anyways If you really want this can be done, simply add a m3u list
with the letter "A" first instead of "O" "eg: A_sputnik.m3u"
and mp3 in mp3 folder, this m3u will be looked first, before the
"O"rbitersound.m3u and the song in it played.
Don't forget to warn the user that it should delete this list if
he want his songs back.
Dan