As far as I know, there are only two problems that can occur, when using the default C172 to create a Cold&Dark situation:
- the mixture: in the C172, you would set it to 0%. But in some jet aircrafts which don't have smart gauges or fuel controls, this can prevent the engine start. You'll have to use the SHIFT+Ctrl+F4 key combo to set the "mixture" control to 100% to allow the jet engines to start. So you might want to leave the mixture in the Cessna to 100% prior to save your defaul flight.
- the avionics switch: a lot of planes, modern or vintage, including payware, do not have an avionic switch in the cockpit. If you set the avionics to OFF in your Cessna and save the default flight, then all of your planes will have avionics OFF when starting a new flight. If your new plane doesn't have an avionic switch, then you'll be forced to use a key combo (to be defined by yourself in the control options) to activate it, which is not nice. I would recommend you to let the avionics switch to ON after you shut down the Cessna and save your flight. It will save you some trouble.
Finally, just like the avionics switch, some planes don't have a generator swich. This is quite rare, but it can happen. So you *might* want to let the generator ON in your default flight as well... I set mine to OFF though..