The enclosure would best be a cheap one, since they're normally plastic, and use a sub-$1 MCU to check the temperature and make sure it doesn't go out of range by dissipating power through a resistor as needed. It won't save power, and you may have to provide more power, but it will save lots of money. using wide-temperature-range (usually selected) components will add a lot of cost. Using the bigger power supply may eliminate some other costs, too, as you probably can undo some of whatever you did to save power.

RE