In this fanfiction, Naruto's character could develop a new sense of purpose. Instead of just aiming to be Hokage, he might also strive to protect the Fem Kyuubi and their special bond. His interactions with her could make him more mature in handling relationships. For instance, he would have to learn to communicate better with someone who has a very different nature from him. This would also make him a better leader as he would be more inclusive of different beings in the ninja world.
Naruto would likely become more in tune with his Kitsune side. He might gain more confidence as he realizes the unique powers it gives him. His relationship with the Fem Kyuubi would also force him to be more empathetic and understanding, as he has to deal with her complex emotions.