Alright....
Each Jinchuriki had certain side-effects from being the host of each Bijuu, correct? Naruto's whiskers, Gaara's manipulation of sand, Roushi's Lava Release, Utakata's use of bubbles etc... Fact of the matter, each and every single Bijuu had some kind of effect on their hosts. Now, would this not be the case for the thing that comprised them? The Juubi. It has all 9 of them inside of it. It must have some kind of effect on any host it has.
If you look at the Juubi's eye, it is a Sharinnegan; which in hindsight is a combination of the ripples of the Rinnegan and the tomoe's of the Sharingan. What is the Rinnegan known for? Being the eye of a god. What is the Sharingan known for? Being the eye of hatred; since it gets more powerful the more hatred the user has. What do we know about the Juubi? Kurama stated he is a God, and it has malice feelings; which if you extrapolate the definition makes it partially synonymous with hatred.
Rikudou had the Rinnegan, correct? How is it possible that a normal human is born with the eyes of the Progenitor of the world? Implausible, and down right impossible. It is said that Rikudou transcended Humanism AFTER he sealed the Juubi within him... Meaning he was a normal human prior to the sealing. Before you say, "How did Rikudou beat the Juubi without a power like the Rinnegan?". Look at what Hashirama has been doing prior to the sealing. His barrier was able to hold the Juubi down, and without Obito's interference, the Juubi would not have gotten out. It's safe to assume even with out the Rinnegan, the Sage was on another level. His sealing weapons alone were immensely power, as shown by the Gin-Kin brothers, who aren't even close to his prowess. The mere fact that he sealed the Juubi means his sealing was basically omnipotent.
Now, refer back to the "AFTER" he sealed the Juubi in him portion. To culminate this, what did I say each Bijuu did to their hosts? Had effects on them. The strongest of them all is bound to bestow power on its host. And this is where Rikudou got his Rinnegan from. Now my "hypothesis" is that, if someone were to get the chakra of the tailed beasts separately, it would culminate inside them to form a "Pseudo" Juubi, or in this case, would probably just make Kurama reminiscent of such, and the effects of it would be the same as the real Juubi; awakening of the Rinnegan. Take into account the Bijuu are what comprise the Juubi, so the effects all 9 of them coming together would have would be largely similar to the progenitor itself.
Also, before you spout the whole "Uchiha+Senju DNA", we have only seen one actual case of someone awakening the Rinnegan; that being Madara. With only 1 person to judge, that isn't sufficient evidence to conclude something as fact. There isn't enough actual "data" to establish it as such fact.
Again, I will reiterate, this is purely theory. I didn't expect somebody to be hostile just because of my beliefs.
