Well, in fanfiction, Luffy's bond with Ace and Sabo is unbreakable. They grew up together and share a lot of memories. When it comes to the Marines, they represent the 'order' that Luffy and his brothers are sort of defying as pirates. Some fanfictions might show a young Marine recruit who has a change of heart after seeing the strong bond between Luffy, Ace, and Sabo. He starts to question whether the Marines are always in the right. Usually, though, the Marines are there to create conflict for the trio.
One interesting storyline could be Ace and Luffy teaming up against a powerful marine squadron. They might use their unique abilities, like Ace's fire powers and Luffy's stretchy attacks, to outwit the marines. Another could be a story where Luffy tries to rescue Ace from a high - security marine prison, facing many challenges along the way.
In fanfiction, a recurring storyline is the Marines' attempts to undermine the brotherly bond of Luffy, Ace, and Sabo. They might try to spread false rumors or create misunderstandings between them. Another popular one is the story of a Marine defector who joins Luffy's crew after realizing the corruption within the Marine ranks. Also, there are stories that focus on the power - up of Luffy, Ace, and Sabo in relation to the Marines. For example, they might gain new abilities and then use them to outwit the Marines in a big battle. There could also be fanfictions that explore the emotional side of the Marines, like a Marine who feels guilty for having to fight against the brothers because he secretly admires their loyalty to each other.
Obviously, Ace and Luffy are the most popular. But other characters like Zoro from Luffy's crew are also often included. On the marine side, characters like Smoker are quite popular as he has a sort of grudging respect for Luffy. Also, Akainu is often included as the big bad marine that Ace and Luffy have to face off against.
Well, 'Luffy and Ace: Unbreakable Ties' is a fanfiction that I really like. It focuses on their childhood memories and how those shaped their relationship as they grew up. There's also 'Ace and Luffy's Great Escape' which is full of action. It shows their cleverness in getting out of difficult situations. 'Luffy and Ace: The True Friendship' is a must - read too. It simply and effectively shows the depth of their friendship.
Well, in this fanfiction, Luffy could interact with the Marines in a more diplomatic way. Since he has the advantage of time travel, he might understand the reasons behind the Marines' actions better. So, he could try to negotiate or make deals with some of the more reasonable Marines. He could offer to help them with other threats in the One Piece world in exchange for them leaving his friends alone at Marineford.
One great 'Ace Protective of Luffy' fanfiction is 'The Unbreakable Bond'. In this fic, Ace is always on high alert to protect Luffy from any threats in the New World. He uses his fire powers in really creative ways to fend off enemies.
Well, one characteristic could be the focus on a more 'romantic' or 'intimate' relationship between Luffy and Ace, which is often not in line with the original platonic nature of their bond in the source material. However, this is a very controversial aspect as it goes against the typical portrayal of their brotherly relationship.
Character development is key. Fanfictions explore how Ace and Luffy grow under Garp's influence. Maybe Luffy becomes more disciplined in some stories, or Ace learns to be more open - hearted, all thanks to their interactions with Garp and each other.
One great 'Ace Sabo Luffy Fanfiction' is 'The Brothers' Bond'. It beautifully explores their relationship, showing how they support each other through various challenges. Another one is 'Sabo's Return'. It focuses on Sabo coming back into Luffy and Ace's lives and how they all readjust. There's also 'Ace and Luffy's Adventure', which takes the three on a fictional journey filled with action and heartwarming moments.