Another interesting concept could be a 'what - if' scenario. For example, what if the Nine - Tailed Fox had a different origin or purpose in the Naruto world? This could lead to a whole new set of adventures and character developments.
One idea could be exploring the relationship between Naruto and the Nine - Tailed Fox in more depth. Maybe showing how they communicate on a deeper level, not just when Naruto is using its power.
One idea could be Naruto having a hard time controlling the transformation at first. He might accidentally cause chaos in the village. Another could be that his friends try to reach out to the Nine - Tailed Fox within Naruto to understand it better. Maybe Naruto starts to gain new powers from the fox that are unique to this fanfic scenario.
One idea could be exploring the relationship between Naruto and the Nine - Tailed Fox in more depth. Maybe Naruto has to enter the fox's mind - scape and they have a long conversation about their fates being intertwined. Another plot could be a 'what if' scenario where the Nine - Tailed Fox was released earlier in Naruto's life and how he would deal with it without as much training. A third idea is to have the Nine - Tailed Fox take on a human form and accompany Naruto on his adventures, causing all sorts of chaos and also some unexpected moments of friendship.
One idea could be a faunus with the traits of the Nine - Tailed Fox being an outcast in the ninja world because of the power and fear associated with it. They struggle to find their place while also having to control the fox - like instincts within them.
In this fanfiction, Naruto could turn into the Nine - Tailed Fox during a time of great emotional turmoil, like when he loses someone close. The transformation is involuntary. As the fox, he runs away into the forest. His friends go on a journey to find him and bring him back to his normal self. Along the way, they discover secrets about the Nine - Tailed Fox's past and how it relates to Naruto.
One interesting fanfiction could be about the Nine - Tailed Fox's origin before it was sealed in Naruto. Maybe it was a powerful and free - spirited being in a different realm, and the story could explore its relationships with other mythical creatures there.
A possible plot for the 'Stiles is a nine - tailed fox' fanfiction is that Stiles' nine - tailed fox form is somehow connected to an old, forgotten magic in the town. There could be a hidden portal or a magical object that only his fox powers can unlock. His friends, who are involved in the supernatural world already, start to suspect that Stiles is different. Stiles then embarks on a journey to learn more about his powers and the history behind them. Along the way, he meets other nine - tailed foxes or similar creatures who teach him about his heritage and how to use his powers for good.
One idea could be exploring how Naruto's relationship with the tailed beasts changes when he has the power of the 10 - tailed beast. Maybe he struggles to control it at first and has to learn from the other tailed beasts how to manage such immense power.
One interesting fanfiction could be where Naruto has a deeper spiritual connection with the Kyubi that allows him to access new forms of power. For example, he might be able to communicate with the Kyubi's past hosts in his mindscape.
One interesting plot could be Naruto fully transforming into the Nine - Tailed Fox during a battle against a powerful enemy. His friends are initially shocked but then try to find a way to bring him back to his senses.
One interesting plot could be Naruto's struggle to control the power of the Nine - Tailed Fox when he releases it. He might have to face inner demons and the fear of losing himself to the fox's power.