One idea could be exploring the Four Tails' backstory more in - depth. Maybe it has a connection to an ancient ninja clan that was long forgotten. Another is a story where the host of the Four Tails has to team up with an unexpected ally to control its power.
In some fanfictions, a cool plot could be that the Four Tails has a unique ability that no one knew about. For example, it can create portals to different dimensions. And the story could revolve around the main character trying to use this ability for good, while others want to misuse it. Also, a plot about the Four Tails' relationship with other tailed beasts in a more personal way, like they have a secret communication system, would be interesting.
One idea could be exploring the origin of the Ten - Tails in a different light. Maybe it was created by an ancient civilization for a noble purpose that got corrupted over time. Another could be a story where a young ninja discovers a hidden power within the Ten - Tails and has to learn to control it without being consumed by its dark energy.
One idea could be a fanfiction where Naruto has to temporarily transfer the Nine - Tails' power to a fellow ninja to save the village. This would create an interesting dynamic as the other ninja has to quickly adapt to the power and the responsibility that comes with it.
Perhaps in the fanfiction, the Zero Tails is a manifestation of the negative emotions of the ninja world as a whole. A group of young ninjas discover this and they try to find a way to purify the Zero Tails. They seek the help of old sages and learn ancient jutsu to attempt this purification, which could lead to a battle against those who want to keep the Zero Tails as a weapon of mass destruction.
One idea could be Naruto having a unique connection with the Nine Tails that allows him to access new forms not in the original series. For example, a form that combines his human features with more fox - like aspects in a more aesthetically pleasing and powerful way.
Well, in this fanfiction, it might be that Naruto's transformation into the four - tails form reveals some hidden secrets about the Nine - Tails' origin. This could lead to a whole new adventure as he tries to uncover more about it. Also, perhaps the four - tails form has a different set of abilities compared to what we've seen before, which makes for exciting battles and challenges for Naruto to overcome.
One idea could be Naruto using the Nine - Tails' power to travel to different dimensions and encounter versions of his friends with different personalities. Another could be him training with the Nine - Tails to create new and unique jutsu that no one has ever seen before. Maybe he uses the power to go back in time and change certain events in the ninja world's history for the better.
One plot idea could be Naruto and the Nine - Tails having a spiritual conversation that changes Naruto's perception of their relationship. For example, the Nine - Tails could reveal some secrets about the Uzumaki clan that Naruto didn't know before. Another idea is that they could team up in a unique way to face a new and powerful enemy in the Hidden Leaf Village. Maybe there's a dark force that can only be defeated by their combined power and a special bond they form.
Well, there could be a fanfiction where the Nine - Tails Chakra has a mind of its own and starts to communicate with Naruto in a more complex way. It could show him visions of the future of the ninja world and guide him to make choices that are different from what he would have done otherwise. This could lead to new alliances and a completely different path for Naruto and his friends in the story.
One plot idea could be Naruto struggling to control the 4 - tails form in a new and dangerous mission. Maybe he has to fight an enemy that specifically targets his unstable state. Another could be his friends trying different ways to help him calm down when he goes 4 - tails, leading to some heart - warming moments of friendship.
Well, a great plot could be about Naruto losing control of his Nine Tails Cloak in a more psychological way. Instead of just being overpowered physically, he starts to have nightmares and visions related to the Nine Tails while in the cloak. This could lead to a journey of self - discovery where he has to face his inner demons as well as the power of the cloak. Also, a story where the Nine Tails Cloak can be used to travel through different dimensions or time periods would be really interesting.