I'm not sure I remember where Kishi ever stated that the Rinnegan required both Senju and Uchiha powers in order to use it. As I understood it, the original Six-Path Sage had two sons. One gained his eyes (i.e. the Rinnegan) and the other gained his physical energy. The son who received the...
I've been a bit suspicious about the EMS ever since Tobi started talking about linking Sasuke with the Gedo Mazo statue. I became even more suspicious now that Kishi is holding out on specifically what Sasuke's EMS looks like. He definitely didn't hold out with Sasuke's regular MS. We've seen...