This is just an idea I had i my head since the end of the series. Kakashi being the Hokage bugs me on a conceptual level. There was no hint Tsunade wanted to relinquish the roll of Hokage save her initial dismissal of the position and she seemed to have great pride in the position during the Pain Assault and the 4th Shinobi War. It also bothers me the leaf village has gone through so many Kage in short span of time.
I do agree Kakashi should have been promoted but it should have been as Jonin Commander since Shikaku died in the war. He would still be integral to the village but Tsunade wouldn't have suddenly step down for no reason.
I also like this idea because I always cared for the idea of Tsunade giving Naruto the Hokage Hat, passing down Nawaki's and Dan's dream onto him herself.