The life of an MOV might be slightly shorter on DC - but not by much.What do you mean by AC, the input is 110Vdc and the output is 24Vdc. Also what is a through hole sub panel. My apologizes, I did try googling that first.
A sub panel is a small PCB separate from the main one, makes it easy to do a one off through hole board without creating difficulties on the SMD assembly.
Its hard to believe this problem is insurmountable.