This might be out of the scope of the project. But I always wanted this to be simulated (in a lot of aircraft a lot of the switches are for the cabin environment). And with passenger and pilot voices a proper feedback could be given to the player.
You can get outside air temperature from the sim, and the positions of the environment controlling switches from the aircraft to come up with a estimated cabin temperature.
Passengers and pilots could play sounds and speech ("its getting cold / it's getting hot in here" ect.)) according to the cabin temp. Like shivering or getting too hot or even getting hypodermic for prolonged exposure to freezing temps. A step beyond would be fogging up the windows in the right conditions (with an effect like the ice on the window)
As I said this might be beyond the scope of FSRealistic, but currently this product would fit best for this kind of stuff.