ghadlock, wish I could help you more.
As you might already know, right now you can see (sort) your music files in detail view/Image File.
This will tell you if the art is "Inside File", "Folder.jpg" and even "[Artist] - [Album].jpg"
This is pretty handy to find all files which don't have the external jpg's.
Edit, just re-read your Q, maybe you didn't know about the detail view and adding the "Image File" column for easy view/sort.
Can't help you on the enmass option, but with urlybird suggestion this could be an option.
Slight hi-jack (almost OT)...
It would be nice if we could get more detail out of the Image file, like dimensions and even embeded art size.
This would really help those who need to keep their art to a certain size due to some players that choke on large album art (older Sansa has a 32 or 28 KB size limit)
Most MC users are not as obssessive as me, but as a quick visual tool for imbeded album art would be very nice to have.
With problematic portible players, knowing which files are 300 x 300 or even 600 x 600 would make it so much easier to sort...
I can always wish in one hand and ...