This seems a non-starter from a few angles. The big question is why would you want to do this in the first place.
There are more appropriate ways to heat an aircraft & I'm pretty sure that there will be a purpose designed heating system.
If you are overnighting on an apron, then you should have ground power available. If you have ground power, then even if you have to use an electric heater then a fixed or portable ground power supply is a more appropriate supply than something thrown into & out of the hold each time you need to use it.
Ultimately, if you pursue this route, please make it a fixed, permanently installed & dedicated APU in a properly engineered, documented, approved, inspected and recorded manner by competent people.