Acually thats a great idea!!!! I don't think you should have any issues as long as the burner is going. Wind or even a light breeze would quickly dissipate any propane that would collect if the burner was left on without being lit. Since propane is heavier than air, you could lift the can a few inches before you light it just to be safe. I would just make sure the hose from the tank isn't rubbing any sharp edges.
Screw it, Lets brew it
Primary 1- BM's Cream of three crops.
Primary 2- Paleface Scalper
Primary 3- Monks Reward (Kreuzberg)
Kegged - Honey Badger, Heady topper clone 1, Indian Paleface Scalper
Bottled- Skeptical Dog winter Lager, Hell's Belgian, Old Dutch Hiefer Hefe,Aphlewein, Chocolate Thunder porter, Jacked up lantern