I don't know what a pop cooler is, but if it has a compressor and you can put some sort of controller on it (Johnson, Ranco, wired-in PID) to regulate the temperature, then the other considerations are air movement to ensure consistent temperature throughout, and humidity control and/or the use of mini-caves. If you don't want to black out the glass door, you could just cut a sheet of insulation board to fit. That would serve the dual purpose of improving insulation and blocking the light.