The problem is that the gas that is going to be squirted out behind the pellet has to sit in the valve and gas tube. The gas might be warm going in if you just heated the tank, but in a few minutes it would be cool again.
Then the gas gets squirted out into a cold barrel...which doesn't do a whole lot for its ability to rapidly expand.
I think it could be done...have played with various ideas....but it will work best if the whole rifle is warmed, but not heated past 80 degrees. Have a lot of electric warmers on the market...gloves, socks, motorcycle seats, portable baby-bottle warmers, etc. Some can be more easily adapted than others, but you really need a thermometer and a temperature control to be sure the gun isn't over heating.