Well, perhaps in the fanfiction, a female character uses the henge to become the Kyuubi to participate in a special ninja tournament. Since the Kyuubi is so powerful, she might have an edge in the battles. But she also has to deal with the fact that the other competitors are suspicious of her sudden 'appearance' of such a powerful form. And there could be a sub - plot where she's trying to master the Kyuubi's powers while in the henge, which adds an extra layer of difficulty and intrigue to the story.
One idea could be a female ninja using the henge to transform into the Kyuubi for a stealth mission. She could infiltrate an enemy base while in this form, using the Kyuubi's intimidating presence to her advantage. Another plot could involve a female character using the henge to look like the Kyuubi to scare off some bullies in the village. Maybe she's a young kunoichi trying to prove herself and this is her unique way of handling the situation.
One idea could be Naruto using his henge to transform into the Kyuubi in a different way than expected. For example, instead of just looking like the Kyuubi, he could also gain some of its powers in a limited form while in the henge. This could lead to him surprising his enemies and allies alike.
One idea could be that the female Kyuubi form uses her unique powers in a way Naruto has never thought of. For example, she might be able to communicate with animals in a more profound way due to her connection with nature as a nine - tailed fox. Another plot could revolve around how she has to hide her femininity while in the Henge form to avoid unwanted attention in the ninja world. Maybe she struggles with maintaining the balance between her human - like emotions and the wild nature of the Kyuubi.
Perhaps a plot where the female Kyuubi has to take on a human form to protect Naruto from a new, powerful enemy. In the process, they develop feelings for each other while fighting side by side.
One idea could be that Naruto uses the Dragon Henge to infiltrate a secret organization that has a dragon as its symbol. He could gather intelligence while in the form of a dragon.
One idea could be the main character, who is a henge master, getting involved in a mission where they have to use their henge skills to infiltrate an enemy stronghold. They could transform into various characters to gather intelligence.
One idea could be that Naruto uses his transformation jutsu (henge) to transform into Latias. He could then use Latias' abilities like flying and psychic powers to his advantage in a battle. Maybe he's in a new, strange land where Pokémon exist and has to blend in by using the henge.
One idea could be Naruto using the Solid Henge to create complex and long - lasting structures for strategic purposes in a battle. For example, he could make a huge fortress that the enemy has to break through, adding an interesting twist to the fight.
One idea could be a character using the permanent henge to blend into an enemy village and discover their secrets. For example, Naruto could use it to look like a random civilian in the Sand Village and find out about their new defense strategies.
One idea could be that Naruto uses his henge to transform into Inari to teach the real Inari a lesson about self - confidence. He could go through a day in Inari's life, facing the same challenges Inari does, but handling them in a more positive way, inspiring the real Inari to change.
Perhaps there's an enemy who is only attracted to beautiful women in swimsuits and Naruto uses the Henge to lure the enemy into a trap. He has to perfect his female mannerisms and appearance to be convincing enough to draw the enemy in. Along the way, he might get help from Ino to style his 'female' look.