Updated both Scripts: 1. Saving from missing Files to an extra Folder is now working perfect. 2. Updated Normal Script saving to alphanumeric subfolders like A/, B/ and so on. Because anything without alphanumeric characters was just saved to the Folder #, i changed that part. If no alphanumeric album artist or artist name (in the case of various artists, album name) is found it just uses the first number, kanji, charakter or whatever it is and create that folder (like 1/ , 8/, ♂/). Just be shure that windows has other language packages installed and can write them. 
Hey there, because Music Brainz Picard Version 2.7 (beta) now supports more than one script i made use of it. I´m Tagging Collections seperately with Foobar2000 with the Tags Collection and Collectiontyp (just select all Files, go to properties, right click, add Tag. The good thing is the search engine in Foobar2000 to find anything for an collection) and than use these Tags in an second script with Music Brainz Picard.
I think that would work for Audio Books, DJ Mixes and the Like aswell because you use your personal Tags as base.
It sorts out Dupes, Incompletes and even Missing Files that cant be found on MusicBrainz, so manually saving is possible.
Collection Script:
/Collections/
$get(collectiontyp)/
$get(collection)/
$get(_extension)/
$if($is_complete(),,
$if($lt($matchedtracks(),%_totalalbumtracks%),_Incomplete/,$if(%musicbrainz_albumid%,_Dupes/,_Missing/)))
$if(%musicbrainz_artistid%,
%originalyear% - $left(%album%,60)/
$if($gt(%totaldiscs%,1),CD$num(%discnumber%,2)-)$num(%tracknumber%,3) $left(%title%,60),
%date% - $left(%album%,60)/
$if($gt(%totaldiscs%,1),CD$num(%discnumber%,2)-)$num(%tracknumber%,3) $left(%title%,60))
My Normal Script looks like this and goes more into detail with Sorting, so feel free to combine them or so
MusicBrainz/
$get(_extension)/
$if($is_complete(),,
$if($lt($matchedtracks(),%_totalalbumtracks%),_Incomplete/,$if(%musicbrainz_albumid%,_Dupes/,_Missing/)))
$if($eq(%musicbrainz_albumartistid%,89ad4ac3-39f7-470e-963a-56509c546377),
$left($if2(%albumartist%, %artist%),50)/
$upper($firstalphachar($if2(%album%, %albumsort%),$if(%musicbrainz_albumid%,$left(%albumartist%,1),)))/
$left(%album%,60)/
$if($gt(%totaldiscs%,1),CD$num(%discnumber%,2)-)$num(%tracknumber%,3) $left(%title%,60),
$upper($firstalphachar($if2(%albumartist%, %artist%),$if(%musicbrainz_albumid%,$left(%albumartist%,1),)))/
$left($if2(%albumartist%, %artist%),60)/
$left(%album%,60)/
$if($gt(%totaldiscs%,1),CD$num(%discnumber%,2)-)$num(%tracknumber%,3) $left(%title%,60))
As a little example: I am tagging the “collectiontyp” Tag with the Tags Compilations, Discographies, Recordlabel, Soundtracks or Divers so adding something like Audiobooks or DJ Mixes as an collectiontyp would be possible.
For the Tag “collection” i am using something like Harry Potter (that would be collectiontyp Soundtracks) or Das Modul (that would be the collectiontyp Discographies) and so on.
