I need to go down this journey too.
Any advice on the storage plate options? E.g., the IsoTherm ASU units? Instead of the evaporator plates?
I currently have one house battery and no solar, I have been told to get into the electric fridge space I need to add a second battery and solar. So I have been putting the inevitable off.
Removing the brine and filling it with expanding foam is a good idea, I always thought it was advantageous to keep the brine as a cold storage plate, now I see the light. Also if I remove the brine then I can drill through the fridge to get access for a a plate, so that's a win win.
One of the fridge kitset suppliers talked me out of the ASU and advised to keep the brine. Now I am going full circle.