Well, perhaps the mouths on his hands are a result of some sort of curse or an ancient jutsu gone wrong. Naruto then has to find a way to either get rid of them or learn to live with them. He could face discrimination from some villagers who are scared of his strange new feature. But he also might find some allies who see it as a unique power and help him explore its potential.
A possible plot could be that the mouths on his hands are connected to a parallel dimension. Naruto accidentally opens a portal through one of the mouths and strange creatures start coming out. He has to figure out how to close the portal and deal with the chaos that ensues. Along the way, he might learn more about the origin of these mouths and how they are related to the history of the ninja world.
One plot idea could be that Naruto discovers he can use these hand - mouths to communicate secretly. For example, in a mission where silence is crucial, he could use the hand - mouths to convey messages to his teammates without making a sound. Another idea is that these mouths have unique abilities, like being able to sense chakra more acutely. So Naruto has to learn how to control and use this new sense in battles.
One possible fanfiction could be about Naruto using the mouths on his hands for a unique jutsu. Maybe he can use them to perform a super - powerful suction technique to draw in opponents or objects. Another idea could be that the mouths have the ability to speak different languages, helping Naruto in his diplomatic missions across different ninja villages.
One plot idea could be that Naruto discovers the Keyblade while on a strange new mission outside of the Hidden Leaf. He initially has no idea how to use it but through trial and error, he starts to unlock its powers. Another idea is that the Keyblade is a gift from a mysterious sage who believes Naruto has the potential to use it to save both the Naruto world and the world connected to the Keyblade. Maybe Naruto has to use the Keyblade to fight against an enemy that can manipulate time and space, which is a new and dangerous threat to his village and friends.
Another plot could be that the Sharingan is given to Naruto as a last - ditch effort to save the village. A dying Uchiha gives Naruto his Sharingan, and Naruto has to figure out how to incorporate it into his already powerful set of skills. He might have to deal with the jealousy or suspicion of some of his comrades who are wary of the Sharingan's power.
A third plot idea is that Naruto is given the Rinnegan as a last resort to save the ninja world. An old sage or some kind of divine being bestows it upon him. But with the Rinnegan comes a prophecy that he will either save or destroy the world. Naruto then has to battle his inner demons as well as external foes, all while trying to understand the true nature of the Rinnegan and its place in his destiny.
One plot idea could be Naruto constantly falling asleep during important ninja missions. His friends initially think he's being lazy or irresponsible, but then they discover it's a medical condition. They start to adapt their strategies to protect him when he's asleep and also find ways to manage his narcolepsy so he can still contribute to the team.
Perhaps Naruto is on a mission in a strange new land where guns are the common weapon. He gets his hands on a couple of guns and has to quickly learn how to use them to survive. His chakra abilities combined with the guns' power make him a unique and formidable fighter in that land. His friends back in the village are initially skeptical when they hear about it, but then they see how effective he can be.
I'm not sure of a specific one, but it could be that in a fanfiction, the mouths on his hands are used to communicate with ancient spirits. Naruto might be the only one who can do this because of some special connection, and it helps him gain new powers and knowledge to protect the village.
A possible plot is that the baby's existence causes a stir in the ninja world. Some may see it as a symbol of unity between the Uchiha and Uzumaki clans, while others might fear its power. Naruto and Sasuke then have to deal with political intrigue as they try to raise their child in a peaceful environment. Also, the baby could inherit Naruto's positive attitude and Sasuke's intelligence, which could lead to some really cute and interesting interactions within the family.
One plot idea could be that Naruto discovers his golden chakra has a special connection to an ancient prophecy. This could lead him on a journey to find out more about his power and how it relates to the future of the ninja world. Maybe he has to unlock different levels of the golden chakra to face new and powerful enemies.
One plot idea could be Naruto struggling to control the power of the curse mark. He might initially be afraid of it, but as he learns more about it, he discovers a way to use it for good. For example, he could use the extra power it gives during a difficult battle against a powerful enemy.