I am electric and use a 15.5 gal Keggle.
My bag is big enough to fold over the outside of the keg. I also have a false bottom screen over my heating elements to keep the bag and the weight off of the element.
I don't have a pump yet but would really like to get one for recirculation to help spread the heat more evenly through out the mash. right now I do it with an old Old Crow jug, pulling from the bottom and pouring back on top. It works, but a pump would be sweet.
I have a pulley system above the keg for lifting the grains/draining the bag. Also hang my hops bag from the pulley during boil.
My exhaust is several small fans in my basement window and works great.
Hope this helps, any questions, feel free to ask.
Later...........TangleFoot-out