Any brewer doing BIAB batches of less than 5 gallons could, depending on the dimensions of his or her mash/brew kettle, conduct the mash by keeping the kettle in the oven. Preheat the oven to 200 F, and once you reach mash temp and dough in, stick the mash kettle in there and turn the heat off after a minute. You'll lose one degree at most in an hour. It's great.
I mash in a 3 gallon kettle and then dunk sparge on the stovetop in a 5 gallon kettle. With that setup, I'm limited to 7.5 pounds of grain for a 3.5 gallon batch. However, a larger, no-sparge mash in the 5 gallon kettle would work too, because the kettle *just* fits in the oven.