Now Implemented!
Description
Have an option to keep the HVAC running up to 8 hours (or perhaps a timer setting).
Competitive/Pricing/Notes
This allows you to sleep in the car comfortably in cold or hot weather. The feature should work both from the battery and if connected and charging. Interior lights would still toggle (would not be forced on or off). The instrument and main screens might go dark until a change in a door or trunk hatch opens or closes.
Status
Implemented in the Oct-2017 software update for all Tesla vehicles as an option to keep climate on using Camper or Dog mode. HVAC can also be turned on via the Tesla app on a phone.
(Suggested by Bjørn and others)
(voting combined from a close duplicate that has been removed)