The thing here is to "focus" as much of the energy of the flame into the pot and eventually the food or water. I can see how something like the Jetboil's "heat exchanger" Fluxring concept might work, but for most stoves the critical thing is to keep the flame within the circumference of the pot's base and to use a good windscreen. Cranking up a stove so that the flames roar up aronud the sides of the pot might cook/boil things faster, but it will use more fuel than a smaller flame. Matching flame diameter to pot diameter and a good windscreen are two simple and critical factors to get right if you want to maximize the efficiency of your cooking system.
I agree but a flame diffuser or flame spreader works against your idea. The heat is going to go up and around your pot no matter what. That just the way heat flow works. It would be better to use something like the
MSR heat exchanger to capture the rising heat that the stove puts out more efficiently then trying to spread the flame out more.