Ha! There is already a mechanism to do this kind of thing in the IDE driver in Linux. I added it decades ago to deal with "EZDRIVE" partitioning software that did something similarly silly with the partition table.

So a possible workaround here simply involves enabling that code, and checking for the specific brand/model of SD Card converter. Done. Try this (attached).

Note that this is safe (aka "inactive") for use with regular drives too.

EDIT: Replaced builder+image with a single combined builder image.