Maybe it's an idiotic idea, but has anyone tried to scan film with an inverted metallurgic microscope?
Or a an upright materials microscope that uses incident light.
Of course with an apochromatic low magnification objective and a proper mirrorless C-mounted.
I know some people mounted microscope objectives on their cameras, but that's cumbersome.
An inverted microscope would allow to micro-move the stage and fine adjust the DOF.

Would that work?