Well, first of all, Naruto's presence with Juubi - like powers would boost the morale of the people in the Attack on Titan world. He could also use his chakra to create barriers to protect the walls from Titan attacks. And his understanding of friendship and loyalty could influence the relationships between the characters in the series. For instance, he might encourage more cooperation between different military branches. He could also potentially find a way to communicate with the Titans, which would be a huge game - changer in the story.
Naruto could change the story by providing new ways to fight Titans. His ninjutsu skills would give the humans an edge. For example, his ability to move quickly and stealthily like a ninja could be used to gather information about the Titans more effectively.
In a Juubi Naruto Attack on Titan fanfiction, Naruto could form an alliance with Eren. Naruto's ability to sense danger and his superhuman strength would be a great asset. He could teach Eren some of his ninja techniques, like how to better control his Titan form. Maybe Naruto could even find a way to use his Sage Mode to understand the Titans better.
The world of Attack on Titan would experience a major transformation with the introduction of Pokemon. Socially, the relationship between people would change as they bond over their Pokemon. There could be Pokemon centers and Pokemarts within the walls. Economically, a new industry would emerge around Pokemon. In terms of combat, as I mentioned before, different types of Pokemon would bring new tactics. Fire - type Pokemon could set the Titans on fire, ice - type Pokemon could freeze them, and so on. Also, the idea of Pokemon evolution could be incorporated into the story. Maybe the more a trainer and their Pokemon fight Titans together, the stronger their bond and the more evolved their Pokemon becomes, making them even more effective against the Titans.
Fem Naruto's superhuman strength, which comes from her chakra - enhanced body, would allow her to take on Titans in close - combat more effectively than the average Attack on Titan character. She could probably leap onto Titans and deliver powerful blows without the need for the ODM gear's blades. Her healing ability, if it exists in the fanfiction, would also be a huge advantage. If a character gets injured during a Titan attack, she could heal them, increasing the survival rate of the soldiers. This would not only change the outcome of individual battles but also the overall morale and strategy of the fight against Titans.
The fanfiction could change the Naruto universe by introducing new threats. With Naruto so powerful, there could be forces that emerge to try and counterbalance his strength. Also, the story could explore different ways of using chakra, as Naruto's merged state might have unique chakra abilities. It could also affect the way ninjas are trained, as they might try to achieve a similar level of power.
He'd change the combat dynamics. His ninja abilities would give the humans an edge. Simple as that.
One possible plot could be that Naruto and his friends somehow end up in the world of Attack on Titan. Naruto's ninja skills would be really useful against the Titans. For example, his shadow clone jutsu could be used to distract the Titans while the Survey Corps tries to attack their weak points. Also, Sasuke's sharingan might be able to see some hidden details about the Titans that the people in the Attack on Titan world don't know. It would be an epic adventure as they combine their powers to fight the common enemy - the Titans.
Well, he could use his ninja skills to fight the Titans in a really cool way. Maybe he'd show the Survey Corps some new combat techniques. For example, his Shadow Clone Jutsu could be used to confuse the Titans while the soldiers attack from different directions.
Modern technology would change the story a great deal. The characters could have access to GPS for navigation during expeditions outside the Walls. Instead of using swords, they might have energy - based weapons that are more effective against Titans. This would make the battles more intense and less about close - range combat.
Well, in a fanfic where Mikasa dies, the relationships between the characters would be redefined. Armin, for example, would have to find new ways to support Eren without Mikasa's presence. And Eren might start to question his own purpose more deeply. Additionally, the fans of the original story would be both shocked and intrigued. Some might be disappointed as Mikasa is a beloved character, but others would be interested to see how the author weaves the new narrative without her. It could also lead to new alliances and rivalries within the story as characters adjust to her absence.
In this type of fanfiction, God could be the link between Naruto and the Attack on Titan world. Naruto could be given powers related to the Titans by God. For example, he could have the ability to control Titans like Eren. His own ninja powers would be combined with these new abilities. He would then have to face challenges in the Attack on Titan world, like dealing with the political situation among the humans and the threat of the Titans at the same time. This would create a complex and interesting story.