Maybe the samurai armour is not what it seems. It's actually a disguise for an ancient and powerful demon. Naruto, thinking he's getting an advantage, unknowingly unleashes the demon. Now he has to team up with his enemies to reseal the demon while still wearing the armour that's now part of the demon.
One idea could be Naruto discovers an ancient samurai armour in a hidden cave. The armour has special powers that enhance his ninjutsu. As he puts it on, he feels a connection to the samurai of old and starts to incorporate their fighting styles into his own. He might use the armour to face a new and powerful enemy that is immune to regular ninja attacks.
Maybe a story about a samurai warrior who is trained by Naruto to use chakra in a new way. The samurai could then use this new skill to defend his village from a group of bandits that are immune to normal sword attacks. It would be a story of growth and friendship between two different cultures in the Naruto universe.
One idea could be a story where Naruto discovers a hidden samurai clan and has to learn their ways to defeat a new powerful enemy. Maybe he has to master their unique sword techniques.
There could be a plot where the ninjas in the Naruto world are being influenced by Aku's dark magic. Samurai Jack, with his unwavering sense of justice, teams up with Naruto and his friends to break the spell. They then travel to Aku's lair to take on Aku directly. Another interesting idea is a world where the Naruto characters are re - imagined as samurai, and Jack has to train them in the ways of the samurai to face a new threat that combines the worst of both their worlds.
One idea could be that the Samurai Girl is on a mission in the Ninja world and crosses paths with Naruto. They initially have misunderstandings due to their different cultures but gradually learn to work together. For example, she might be tasked with retrieving a stolen samurai artifact that has ended up in the hands of a rogue ninja. Naruto, being the helpful and curious person he is, decides to join her in the quest.
Well, for a 'naruto raised by samurai' fanfiction, the story could start with Naruto being found by a group of samurai. They would raise him as one of their own. Naruto would grow up learning the ways of the samurai, like how to handle a katana and the importance of loyalty. This would lead to interesting interactions when he meets shinobi later. He might have a different view on the ninja world, perhaps seeing some of the shinobi ways as unethical compared to the samurai code.
Perhaps the plot could start with Naruto finding an old, tattered scroll that shows the adventures of Samurai Jack. Naruto becomes obsessed with Jack's story and starts to train in a way that combines his ninja training with what he thinks Samurai Jack would do. As he progresses, he starts to have visions of Jack's world. Eventually, he finds a way to cross over. In Jack's world, Naruto uses his ninjutsu in creative ways to help Jack in his fight against Aku. In return, Jack teaches Naruto the art of the samurai, and Naruto brings these new skills back to his own world to face his enemies in a different way.
One really cool plot twist is when Kagome's time - traveling device malfunctions in a way that she can't go back immediately. This forces her to fully integrate into the samurai society and make a life there. She has to deal with the consequences of her actions in this new world, which often leads to a great story development.
One interesting plot twist could be that Naruto discovers he has a hidden power from a long - lost clan that changes the course of the final battle. This power might be something that gives him an edge against a seemingly unbeatable foe.
A great plot twist could be that Naruto turns out to be a half - vampire. It would completely change his character arc and how others in the Naruto world perceive him.