The problem with most ark designs that they either lack head room , space or both.. i dont see why i tractor couldnt be used as a brooder , given you got a electric hook up to it. THe biggest issue is the risk of fire in the coop when running electricity to it. How many chicks are you thinking of ? if its only a few a large clear storage box , like a rubbermaid would do. Just cut a large hole in the top and cover it with hardware cloth . You can keep them in the laundry or bathroom.