Just a thought...
What if Madara Uchiha is only a mass of his own chakra, without his own body?
I'm gettin the idea from the composition of Bijuu, as they are just masses of chakra, but have shape, thought, and form.
If I could put my 2 cents worth, I would probably say that his Eye of the Moon plan would be for him to acquire the Combined Chakras of all of the Bijuu, making a new form for himself to take-over...creating the ultimate being.
As far as we know, chakra can be used for pretty much anything, it can be contained, freed, and can be shaped into any form with the right amount of control.
This is just a theory after all.
Either Madara has/n't a body, or he's just wearing that get-up to hide his uggo-factor.:p