In the past chapter sasuke said he would give his left eye to kakashi if he died but that doesnt make sense unless naruto is with kakashi all the time.
We already know that a simple 3 tomoe sharingan drains a lot of his chakra, during the war he got better even to the point where he could use kamui like 3 or 4 times in a row before running out of chakra, but even so nagato coming from the uzumaki clan which were known for having huge chakra pools, nagato was drained so bad of his chakra that he looked like an elder being at his early thirties, obito who was had uchiha blood and half of his body was made out of hashi´s dna said he had trouble with the chakra drain.
That´s why i dont think kakashi can handle a rinneganon his own, one single use would send him right away to the hospítal, if he wanted to use the rinnegan he would need to make naruto his right hand so whenever he needs to use it naruto will give him the chakra needed plus naruto has senjutsu so that must make it easier.
