> Here in Unix I can just mount archives and disk images.

This is so true! And it's much easier than just having the music player support zip files. Especially for zip-in-zip like GP described. Can you imagine double clicking an archive and have it play, rather than simply do:

    cd Downloads/
    ls
    mkdir tmp
    mount-zip myfile.zip tmp
    ls tmp
    mkdir tmp2
    mount-zip tmp/myinnerfile.zip tmp2
    audacious --new-instance tmp2 --play
    while killall -0 audacious; do
        sleep 1
    done
    umount tmp2
    umount tmp
    rmdir tmp2 tmp