First, Naruto's ability to move at high speeds could be very useful. He could quickly reach Ace before the execution. His chakra could be seen as a sort of 'energy' in the One Piece world. His ninjutsu like the fire - style jutsu could be adapted to fit the more 'nautical' environment. For example, instead of normal fire, it could be some sort of 'sea - fire' that can even work underwater. Also, his summoning jutsu could bring in some powerful creatures to help in the fight against the Marines.
Naruto's shadow clone jutsu could be used in a similar way as in his own world. He could send clones to gather information about the situation at Marineford, like where Ace is held and what the Marines' plans are. His rasengan could be a powerful attack against the Marines. Maybe in the One Piece world, it could be seen as a type of 'haki - infused' attack since haki is the main power source there.
In the fanfiction, Fem Naruto might have some sort of special connection or knowledge. Since Naruto has a strong sense of justice, Fem Naruto would be the same. She might have heard about Ace's situation through some channels and decided to take action. She could use her chakra - enhanced strength to break through any barriers the marines set up to keep Ace captive.
It can be considered popular. Fans are always interested in crossovers that bring together different beloved universes. In this case, Naruto's overpowered abilities in a setting like Marineford from One Piece create a lot of possibilities for creative and action - packed storylines. The idea of him saving Ace, a significant character in One Piece, adds an emotional and exciting element to the fanfiction concept.
Naruto's ability to create shadow clones would be extremely useful in the One Piece world. He could send clones to gather information across different islands while he and the Straw Hats are on their main journey. His Rasengan, being a powerful concentrated attack, could be used against tough enemies like the Yonko's commanders. And his immortality means he can keep using these abilities without the fear of death, making him a very formidable ally in the One Piece universe.
Naruto's Rasengan could be seen as a super - powerful attack similar to some of the advanced Haki techniques in One Piece. His ability to create shadow clones would be a huge advantage in battles and also for things like scouting or distractions. His chakra control could potentially be related to Haki control as well. And his immortality would make him a very unique and feared presence in the One Piece world, as most characters there are not immortal.
Well, Harry Potter might be magically transported to the 'One Piece' world just in time to save Ace. He could use his Patronus charm to fend off the attackers at Marineford. Since his Patronus is a powerful form of positive magic, it could be strong enough to hold off the Marines for a while. He might also use his knowledge of potions to heal Ace if he's already injured. And perhaps he forms an alliance with Luffy and the Straw Hats to help them get out of the dangerous situation at Marineford.
Yes, there might be. The 'Harry Potter' and 'One Piece' (where Marineford is from) fanfic communities are quite large and creative. There could be a crossover where Harry Potter somehow saves Ace at Marineford. You can check fanfic platforms like Archive of Our Own or FanFiction.net to see if such a story exists.
In this fanfiction, Ace, Luffy and Sabo could have a future in Marineford that is full of hope. Maybe they work together to change the perception of pirates in that place. Ace could use his fire power to protect the weak, Luffy with his unwavering will continues to inspire others, and Sabo with his intelligence devises plans to make Marineford a more inclusive place for both pirates and marines.
Well, Naruto's chakra - based abilities would be quite unique in the One Piece world. His Rasengan, for instance, would be a powerful new type of attack that most characters in One Piece haven't seen. His ability to walk on walls and water using chakra would also give him an edge in many situations. He might also be able to use his chakra to sense things in a different way than the Haki users in One Piece, which could be a big advantage when exploring islands or looking for hidden treasures.
Naruto's ninjutsu skills could be very powerful in the One Piece world. His Rasengan, for instance, is a concentrated ball of chakra. In the One Piece world, it could be as strong as some of the more powerful Devil Fruit attacks. His ability to run up walls and trees using chakra control could also be useful in the more diverse terrains of the One Piece world, like running up the side of a ship or a rocky island.
Naruto's Rasengan could be used in a similar way as some of the physical attacks in One Piece. For example, it could be as powerful as Luffy's Gear attacks. Also, his ability to jump great heights and distances might be on par with some of the Zoan Devil Fruit users' enhanced physical abilities.