Hi rern,
A followup on how the Enhancements have been handling my USB drive:
I tried the Addons with the new .05 image from janui/gearhead and I had the same problems with the USB drive mapped to LocalStorage via fstab that I described before.
Then I decided to map the USB drives in fstab to /mnt/MPD/USB and it worked! The drive appeared in the Library and its contents were accessible and playable.
I also added a file directly to LocalStorage on the SD card, and it still was not accessible from the Library. The Library item count for SD showed zero, and clicking on it did nothing.
It seems that there might be something going on with how the enhancements handle files in LocalStorage, but there is no problem when the same files are in NAS or USB.