The solution at present is to mount an image with IMGMOUNT in an SVN build. Some might find that inconvenient if they don't have software to create bin/cue images that preserve the meager few audio tracks these games have. Because there is a solution, fixing MOUNT seems less important given its complications, but of course it would be nice to get it working.

A more radical approach I thought of was removing the disk cache from the equation, and creating a "local_drive_nocache" drive type for cdroms, but that appears to be a project in itself, and the issue of "first" probably still remains.

How about if they mount a real CD-ROM? Maybe you could handle that in such a way it would work.

Years ago I wrote a dos shell program that used lfn services provided in win95. http://www.larsdennert.com/software
If lfn was not available it would switch back to 8.3 which is what happens in dosbox. If anyone needs a dos shell, feel free to use it. You'll notice that if you run it in windows (32 bit of course) it will display lfn's.