He could become a weapons master through some kind of special power-up. For example, a new chakra form that gives him an affinity for weapons. He might be able to infuse his chakra into weapons, making them more powerful. And Naruto is known for his hard work, so he'd surely spend countless hours training with various weapons, from swords to shurikens, until he masters them.
He could start by training intensively with different weapons under the guidance of some old and experienced ninja. They might teach him the proper techniques and stances for using each weapon effectively.
If Naruto were a master of the force in fanfiction, it would change the whole Naruto universe. He might be able to levitate and move objects with ease, which could be a huge advantage in battles. His rasengan could be infused with the force, making it an even more devastating attack. And he could potentially use the force to communicate with others telepathically, adding a new dimension to his relationships with his friends and allies.
Well, it depends on the specific fanfiction. There are countless fanfictions out there, and while many might explore the idea of Naruto as the master of Caster, others may not. Some fanfic authors like to create unique power dynamics and relationships, and this could be one of them. However, not all fanfictions will follow this concept.
Another aspect is new power developments. Since there's a master involved, Naruto usually gains new and unique abilities. It could be a special type of chakra control or a new jutsu that the master imparts. In many fanfictions, this leads to Naruto being able to take on stronger opponents and change the course of battles. Also, these fanfictions often have a different take on the Naruto universe's lore, expanding on it in creative ways related to the master's teachings.
It could lead to some really interesting plot twists. Naruto's new ability as a seal master might give him an edge in battles and change the dynamics of his relationships with other characters.
Well, in some fanfictions, Naruto might obtain the Master Sword through a strange portal that connects his world to the world where the Master Sword exists. Maybe he's on a mission and stumbles upon it by accident.
Sasuke could be one. Since they have a long - standing rivalry, Sasuke, with his own powerful skills, would be a great opponent for Naruto now that he's a master swordsman. They could have an epic battle where sword meets sword and their respective powers clash.
In this fanfiction, Naruto could master shurikens in a new way. Instead of just throwing them, he could learn to control their flight path precisely with his chakra. Another weapon he might master is the naginata. It's a long - handled weapon that he could use to keep enemies at a distance while also delivering powerful blows.
It might not be extremely popular in the mainstream Naruto fanfiction world. The idea of Naruto as a 'dark master' goes against his original character traits in the official series. Most Naruto fanfictions tend to focus on his growth as a hero or his relationships within the ninja world.