There are 2 good things about using at least 2 light bulbs. 1st is it's easy to tell if they are working and 2nd is if one burns out you got another working as a back up.
I run both systems I mentioned in the earlier post and I like both about the same.
I'll try to get what I'm thinking drawn up and post a pic or two. You may be better off using a couple light bulbs for heat or a fan/heat combo unit from incubator warehouse.
The freezer space sounds like it would be perfect for the fans and heat source. Take the door off the freezer part letting it be open into the fridge part. Your humidity pans can go at the very bottom of the fridge and 2 turners in between. Any thoughts on the type of thermostat you want to use?
Does she have turners or racks to go in it yet? As far as freon and such, not sure I'd mess with getting rid of it or the compressor. Unless you decide to use the existing fan system. I would use a shelf system to isolate the heat source and fans. How many eggs are you wanting to incubate at a...