I think we are talking about different things here. Lets start with a magic system that cools the hotside to a constant 30c regardless of load. To get a COP of 2 you are limited to a dT of around 15c. This means with no thermal resistance (not possible) the cold side loop would be 15c (ie probably just above dew point for me). these are the kind of numbers I was playing with in my system.

Now lets say you want to reach zero. Now you need a dT of 30c (actually more because of the extra heat form the pelts but we will assume you can compensate). Now you get a COP of around 0.75. In reality with the added heat load you would probably only get 10c cooler for 2-3 times the power. It just doesnt seem worth it to me.