I have another idea. A thick neoprene case with a male velcro tape on its back and two internal pockets inside for chemical hand warmers, which offers free access to screen, main button, power supply and security strap could also do the job. It would be cheap, solve the problem of mounting on a cockpit, spare the remove of the solar panel, protect the device from impacts and doesn't affect the "time to market" of the instrument itself.
Second idea: we've aleready talked about an alertnative back cover (instead of the removable solar panel) which cab be outfitted with velcro tabe to mount the device on a cockpit. Stick to this idea but make it hollow so that one can insert one or two hand warmers in it. This would also solve the problem for exposed use in deep temperatures.
Third idea: if you only like to offer the thick neoprene case with velcro but w/o heat warmer pockets (less elegant) one could still remove the solar panel and put one or two heat warmers in its place before putting the device in the case. Would still be helpful, and I think that everybody could profit from a thick neoprene case.
In either case: please ship this case before autumn comes since we're already flying below 0° then.