That was a complicated solution, for sure, but kudos to the poster for having the courage to deal with udisks-glue. 
I managed to try out my hacky workaround in /etc/fstab – and it works. The classic one-liner!
osmc@osmc:~$ grep dummy /etc/fstab
UUID=c91adeb7-28d9-434a-99bf-b6aa283e2d9e /mnt/dummy ext2 noauto,nofail 0 0
osmc@osmc:~$ blkid
/dev/mmcblk0p1: UUID="A269-73B7" TYPE="vfat" PARTUUID="a13c9b62-01"
/dev/sda1: UUID="c91adeb7-28d9-434a-99bf-b6aa283e2d9e" TYPE="ext2" PARTUUID="9fce7055-01"
/dev/mmcblk0: PTUUID="a13c9b62" PTTYPE="dos"