Re: Just a thought and what if's
Just to clarify my theory:
I think after Madara discovered a injured Obito and was in the process of healing him up, he was trying to figure out ways to control him in the future. The first part of his brainwashing was done verbally, by telling him his theory on the darkness of the shinobi world. At the same time Madara ordered Zetsu follow Obito's friends hoping to find an opportunity to exploit to drive the brainwashing to heart. That Zetsu would coincidentally stroll across Kakashi and Rin in trouble is way to damn suspicious to be true. That he would help Obito to escape the lair while keeping the fact from Madara is even more suspect.
Just in case Obito ever began to have doubts he planted that black rod thing inside of him that he claimed was "his power", so that he could take control of him if need be. Being even more cautious and not wanting anything to go wrong, he acquired some of Rin's DNA to Edo tensei her back to life knowing that she was the only person Obito would never betray.
Assuming obito can use the powers of the 6 Paths in this form, there may even be a chance he can revive Rin to true life, which Madara will definitely hold over Obito. Perhaps with the power of the outer path, or maybe by the consuming of the Edo clone by Naraka paths healing ability thus "spitting" back out a revived person.