Has anyone put a switch on a refrigerator defrost heater?

It is like regeneration mode on modern diesels. You don't want it to click uphill.
I think the best way would be program the controlled to not go into defrost at those days. Household refrigerators have never been intended for it, but I would start with giving manufacturer a call and ask for engineer.
They might want to charge you for advise, or maybe hoping for more buyers will provide free help.
Doug is right that putting just a switch you will fool the computer with hard to predict consequences.