One idea could be that Naruto, with the power of the Sage of the Six Paths, gets transported to a different ninja world. There, he has to team up with new and strange characters to fight against an evil force that is threatening both worlds. Maybe this new world has different chakra rules and Naruto has to adapt quickly.
A really cool plot might be that in the crossover fanfic, the Sage of the Six Paths Naruto discovers a hidden prophecy in this new world. The prophecy states that he is the key to unlocking a long - lost power that can save both his original world and the new one from a coming cataclysm. So he embarks on a journey to find the components of this power, facing various trials and enemies along the way.
One idea could be Naruto traveling to a different universe where the Sage of Six Paths is still alive and they team up to face a new, powerful enemy. Another could be a fusion of their powers in a strange way due to a magical artifact in the crossover world. Maybe Naruto gets to learn new jutsu directly from the Sage in a more in - depth way than he did in the original story.
One interesting plot idea could be exploring how the reincarnation affects the balance of power in the Naruto world. Maybe the reincarnated character has unique abilities that disrupt the existing order among the ninja villages.
One interesting plot could be about Naruto exploring more of the Sage of Six Paths' untold teachings. For example, he discovers a new jutsu that was lost in time but was once known to the Sage. This could lead to him becoming even more powerful and facing new threats in the ninja world.
One idea could be exploring the training of Naruto by the Sage of the Six Paths in more detail. Maybe the Sage could teach him some long - lost jutsu. Another idea is to have Naruto travel back in time to the era of the Sage and witness the creation of ninjutsu first - hand.
One interesting plot idea could be that Naruto and Sasuke have to go on a joint quest assigned by the Sage of Six Paths in a dream. They are sent to a parallel universe where the ninja world is ruled by dark forces and they have to find a way to bring back the light. Another idea is that the Sage of Six Paths gives them new powers that they have to master together to defeat an ancient evil that has been awakened. Maybe they also have to deal with their own inner demons during this process as the new powers also come with some psychological challenges.
One idea could be Naruto having to face an ancient evil that threatens to disrupt the balance between the six paths and the avatar world. He might have to learn new jutsu inspired by the avatar elements. Another could be Naruto forming an alliance with avatar characters to fight a common foe, like a powerful dark spirit that can cross between their universes.
Perhaps a plot where Naruto has to teach the Sage of Six Paths Senjutsu to a new generation of ninjas. This could involve dealing with their different learning abilities and personalities, and also facing threats from those who want to misuse this powerful technique. It could also show how Naruto has grown as a teacher and a leader.
One idea could be exploring the backstory of the Sage of Six Paths in more detail. Maybe his early life, his training, and how he came to be the powerful figure he is. Another plot could involve a modern - day ninja somehow getting in touch with the power or spirit of the Sage of Six Paths and having to deal with the consequences. For example, they might gain new abilities but also attract dangerous enemies.
One idea could be Naruto from the Six Paths Sage mode getting crossed over into a modern-day world. He could use his powers to fight against new types of villains like super - powered criminals. Another plot could involve a crossover with a different anime universe, like Naruto meeting characters from One Piece and having to team up to stop a common threat that endangers both their worlds. Maybe a powerful ancient evil that has the ability to disrupt the balance of chakra in Naruto's world and the Devil Fruits' power in One Piece's world.
Perhaps a plotline where Naruto uses his new status to bring about true peace in the ninja world. He could start by uniting all the hidden villages in a more profound way than ever before, sharing the secrets of the Sage of Six Paths to promote harmony and understanding among different ninja clans. This would involve complex diplomatic efforts and also dealing with those who oppose this radical change.