A lot of people would disagree with you on the point of buying one, but I agree that it can be useful, it will be good to tinker with one that already works. Saw you point on the Battle Ratz too and I would suggest that they are not going to able to be converted into featherweights, but if its just something to tinker with you're looking for then that might be good. You could maybe even get hold of the instruction book for them and see how it all works by working backwards so to speak.