Just like madara has the 1st hokage DNA, Naruto could have the rinnegan given to him. Afterall, he is an Uzamaki! Hear is a very most point to remember, Uchiha, Senji, and Uzamaki all come from the same family line - SO6P. They all share the same DNA. Madara is trying to force himself to become perfect. If naruto finds a way to become perfect naturally, he may create something more powerful then the rinnegan. I mean, what happens if a ninja is able to balance kyuubi chakra, natural chakra, physical chakra, and spiritual chakra together. Maybe that's true ninjutsu perfection.