Madara mentioned two opposing forces working together. The forces were his Senju Cells and his Uchiha Cell. The Sage were both Senju and Uchiha. If he could have both in a real body, without his eyes what could become of him? That could explain how he absorbed Amaterasu. That could also be how he gained the rinnegan before his death, stealing Hashi's cells. Obito had the power of the Sage, now he has the Sage's body. He's soon going to get both and become the real sage.
1. The sage was not Senju, nor Uchiha, they are descended from him.
2. He already has Senju + Uchiha DNA in his body (what are you getting at?)
3. He awakened the Rinnegan legit, the Rinnegan is a mutation and would surely affect the entire body.
4. Rinnegan allows you to absorb chakra...
5. We already know how he awakened Rinnegan, why are you trying to use already established facts as theory?
6. Obito HAD nothing of the sage, all he had was that he was the 10-tails Jinchuuriki :S
7. Obito is pretty much dead, stop clutching at straws, he's the martyr of the war.
8. If anyone is close to having the Sage's body and power, it's gonna be Madara, he has Senju AND Uchiha DNA, he also has the Rinnegan, the only thing he's lacking is some dirty giant slug/flower/sea urchin/I don't know what the **** that thing was meant to be 10-tailed beast inside him.