I'm looking at a direct exchange DX ground source heat pump. The ground loop is copper tubing with R-410A. Why wouldn't be better to run the refrigerant through an air-source coil before it goes to the ground loop? The air is always going to be warmer or cooler than the refrigerant as it is heading to the ground loop. Wouldn't a greater heat transfer surface increase the efficiency of the system? There are many hours during the year that the air would be at a higher temperature than the ground when heating, and vice versa when cooling. Also, it would help keep the ground from getting thermal saturation. I suppose that controls could be added to bypass the air coil if it started to collect frost. Is this too simplistic thinking?