So TLDR is you are cooling the hot side of it with water and then that water goes through the pipes underground. As its even hotter you are going to lose more temp to the ground - realistically you wouldn’t even have to go as deep for something like this surely? Though you do want a decent surface area for all the pipe.

I did have this sort of thought a while back, but I was thinking of getting a water source heat pump instead and found not many options. Modifying a cheap unit may not be too hard, shitloads of silicone around as much of the hot part as possible.