Stuffed pumpkin on a burner I have been asked to make a main for a potluck this Halloween and I thought I would be "clever" and bake a lamb stew in a pumpkin. I plan to hollow out the pumpkin and add meat, veg, spices, etc. and then replace the top and poke a small hole in it to let air escape.

The main problem is that my oven isn't working properly and don't want to risk it failing halfway through.  Would it be possible to wrap the stuffed pumpkin in tinfoil, and put it over a gas burner on low?  I have plenty of time and could let it slow cook for hours, but I have my doubts on if the technique would work.
I don't think this will work very well. Burners are unidirectional heat sources; the bottom will overcook and the top will be raw. The constant rotating you will need to do will be annoying at best. Ovens provide heat surrounding the entire item, which is why roasting works. I suggest borrowing an oven.

Bear in mind that roasting the pumpkin will compromise its structural integrity. Not roasting seems like a wiser course if you intend it only as a serving vessel.