Im kinda thinking that the third Coffin Hiruzen sealed, was madara. Kabuto stated that Orochimaru experimented on madaras body and to make him complete " this way" he sure must have been alive, cuz to implant an dead body this Power would not really work(to make the edo Tensei complete). This would kind of prove that madara was alive far longer then nagato, and im thinking about the first question that madara gave Kabuto.
"Who is controlling this (Edo Tensei) Jutsu" what if he thought of Orochimaru? I also won't belive that tobi would be able to know anything about that jutsu~ Maybe Tobi,Madara & Orochimaru were partners, but Oro betrayed madara , then tobi betrayed madara by not reving him back. As we know Oro also wanted to crush leaf~