Obito cant use rinnegan.No Obitto's gonna do it Kakashi doesn't need a redemption .
Unless if he finds a way to control the black zetsu which is unlikely i think.
Kakashi using it is probably because his character already comes to an end and he vowed he would do whatever it takes for Naruto to succeed that was the motivation of his life.
So Kakashi indeed would be capable of sacrificing himself to revive Naruto and Sasuke.