One possible plot twist could be that the person who denies Naruto has an ulterior motive. Maybe they are being controlled by an enemy ninja who wants to keep Naruto from having power in the village. Another twist could be that Naruto discovers a hidden prophecy that says his true destiny is not to be Hokage but to lead a different kind of revolution in the ninja world.
Well, one plot twist could be that Naruto is denied Hokage because of some false accusations against him. As he tries to clear his name, he uncovers a conspiracy within the village that goes deeper than he thought. Another twist could be that the village decides to abolish the Hokage system altogether just as Naruto is about to be named Hokage. This throws Naruto into a state of confusion, but also gives him the opportunity to re - imagine what leadership in the village could be like. Also, it could be that Naruto is denied Hokage due to a mysterious power that is influencing the decision - makers, and Naruto has to find a way to break that power's hold to prove his worthiness for the role.