If the problem is depth of field, I suggest looking for a solution with movable planes, like a view camera, that allows you to use the Scheimpflug law.
Some bellows exist that allow you to turn - in the sole domain of macro photography - you camera in a "view" camera, with all movements. I think some of those, for 135 format, even have support for automatic diaphragm mechanism (diaphragm stays open for focusing and closes automatically when you take the picture).
Those bellows should exists both for 135 and 120 film cameras, but I suspect they are easier to find for 135.
I never used them so I am only giving a theoretical suggestion here.