I don't know if this would work or not but no one else has suggested it
(perhaps because it is silly?) but I would enlarge the openings between the
freezer and the refrigerator.
As I understand it, the thermostat is in the refrigerator, and the
compressor works to keep the refrigerator at the right temperature. The
compressor is in the freezer, and the freezer temperature is set by
regulating the air flow to the refrigerator; a lot of air flow is high
freezer temp, little airflow is low air flow. If you removed the wall
completely, the whole unit would be at whatever you set the refrigerator at.