Okay, so we all know that Edo Tensei is used to resurrect a deceased shinobi by sacrificing bodies to serve as a vessel for the soul of whoever is being resurrected; that means that means that the body in the coffin cannot be Madara, because he didn’t die, or so I think. It’s impossible for Kabuto to resurrect Madara when his soul is in Tobi’s body. He cannot possibly be anyone else, for he knew much information about the Uchiha and its history, including Rikudo’s apprentice, the one who was said to originate the Uchiha clan’s hatred and destined battle with whoever holds the will of fire, for example, Naruto and Sasuke.
Second, there is no way Tobi is Izuna because it was stated that Izuna loss his life in battle after the removal of his Mangekyou. Same thing for Obito, he was also confirmed to be deceased. Again, in Naruto Chapter 404, Tobi takes off his mask, revealing his face to Kisame. Right away, Kisame knew who he was, a former Mizukage, Madara Uchiha. So that’s proof that Madara still has his physical body and soul and is Tobi.