The new teacher could also be someone who has a special connection to Naruto's family. In the fanfiction, this could mean that the teacher reveals some long - hidden secrets about Naruto's parents. This knowledge could give Naruto a new motivation or even a new power source. Also, the new teacher may help Naruto in his emotional growth, teaching him how to better handle his anger and loneliness that sometimes surface.
Well, the new teacher in the fanfiction could be from a different village or have a secret past. The new teacher might introduce Naruto to a whole new world of ninja knowledge that he didn't know before. For example, some ancient ninja arts that were lost in Konoha but preserved in other places. This could change Naruto's perspective on being a ninja.