Board Thread:Theories and Speculation/@comment-1512913-20150827121154/@comment-5407586-20150828080400

Elveonora wrote: JOA20 wrote: Hagoromo's chakra is the combination of Indra's and Asura's. Madara/Sasuke have Indra's chakra, Hashirama has Asura's. Itachi and Izuna, while not being Indra's transmigrants, are still his descendants, so I think their chakra can be considered as an extension of Indra's. With that mindset, lets consolidate it even more and state that all chakra is Kaguya's thus everyone has a piece of Kaguya's chakra. According to her, yes http://images1.wikia.nocookie.net/__cb20110904041912/messaging/images/c/c2/Emoticon_silly.png

But, once Madara turned Izuna's Mangekyō into his own Eternal Mangekyō, the eyes became his own, same for Sasuke with Itachi's eyes: it was Madara/Sasuke, not Izuna/Itachi, who awakened the new power, so only they can use it to the fullest. But I agree that, were Izuna/Itachi to regain their original eyes, they'd be the best users after those who evolved said eyes.

About the Rinnegan, unless Izuna/Itachi got some Senju DNA implanted, I don't think they could use it as effectively as Nagato or even Obito. At Madara/Sasuke's level, no. IMHO.