Kirk,
Dust-off images are usually done when I start a shoot and when I end a shoot and, if I remember, when I change lenses. So they are not necessarily associated with one file, but a set different files. When I get to sorting, etc, I have many times moved images using PM and have forgotten that there were .ndf files in the same folder, then deleted the folder. Opps.
So the need is was really around displaying a "image" for .NDF files so I now that special type of .NDF file existing and need to deal with it.
Your idea of associating other files with an image is interesting. It could be considered that any images with the same filename, but different type should be considered a PM does with NEF + JPG. (e.g. image01.NEF, Image01.JPG, Image01.TIF, Image01.PSD, Image01.NDF, etc.) Like stacking all related files into one contact sheet thumbnail.
I guess I can dream.
Thanks.