What you said about rinnei tensei is stupid. So, he will kill for instance Sakura and then at some moment he will say with a trollish face "you're good" and he will sacrifice himself to bring her back just to tesst him?
Well maybe I was wrong about that but it was just a thought. Its really the only way to truly test naruto's morals who is suppose to be the ultimate good guy. So by killing somebody he will make naruto want to kill him but if he does then the cursed world of hatred/killing wont end because even naruto can be pushed to kill even if it his best friend.
And with the info we have by reading and on the wikia I thought he might be able to use rinnei tensei.
Konan was worried about naguto using it only because of the fact he had very little chakra.
Obito was in a different situation though because he is reviving somebody long dead/edo tensei which would take alot more chakra which is why he would die. Even after he did revive madara he was still alive for a while even though he just had lost the 10 tails.
And neither of them owned the rennigan personally which sasuke does and on a different level.
Sasuke and naruto could also work together to revive them with yin/yang powers because we already seen that naruto healed both gai who was suppose to be dead and give obito some life back.