One idea could be exploring Ace's memories of his time training with Whitebeard. Maybe show some of the tough lessons he learned and how he grew closer to his crewmates through those experiences.
A possible plot could involve Whitebeard seeing Ace's memories of his past and realizing how much pain Ace had carried. This could lead to a heart - to - heart moment between them, strengthening their bond even more. It could also show how Whitebeard becomes more protective of Ace after seeing his memories.
Their relationship can be shown as a father - son type. Whitebeard being the protective and wise father figure, always looking out for Ace. For example, when Ace is in a fight, Whitebeard is there to back him up or give him advice based on his own experiences.
A plot could revolve around a tournament on an island. Ace, Sabo, Luffy, and members of Whitebeard's crew participate. The prize is a powerful devil fruit. Each character has their own reasons for wanting it. As the tournament progresses, old rivalries are rekindled, new friendships are formed, and they all discover more about themselves and their place in the pirate world.
One common theme is the bond between them. Fanfictions might explore how Ace's relationship with Luffy and Whitebeard affected his decisions and growth. Another theme could be adventures that they might have together that weren't shown in the original manga or anime. For example, they could go on a special mission to a new island.
One interesting story could be about Ace's adventures before joining the Whitebeard Pirates. Maybe he has some encounters with unique sea creatures or discovers a hidden island. Another could focus on his relationships within the crew, like his bond with Marco. There are also fanfictions that might explore Ace's training under Whitebeard and how he grew stronger.
Well, perhaps in the fanfic, there could be a plot where Whitebeard decides to train Ace, Sabo, and Luffy in a new form of combat. This training could lead to them developing new powers or techniques. Also, they might get involved in a political intrigue within the pirate world while associated with Whitebeard. Like, they have to deal with other pirate lords who are jealous of Whitebeard's influence and try to undermine him by targeting the three brothers.
One idea could be Naruto having Whitebeard's sense of honor and leadership in the ninja world. He might gather a group of ninjas similar to how Whitebeard had his crew, and they fight for justice and protect the weak. Another plot could be Naruto having to deal with Whitebeard's old enemies reincarnated as well, leading to epic battles.
One idea could be that Luffy and Whitebeard's crews team up for a common goal, like fighting against a new and extremely powerful enemy that threatens the whole world of pirates. Luffy's carefree and determined nature could contrast and also complement Whitebeard's more fatherly and protective leadership style.
A great plot for Ace Combat 3 fanfiction might be to create an alternate timeline. In this timeline, a major battle from the game was lost instead of won. This would change the entire political and military landscape of the game world. Pilots would have to deal with a much harsher reality, and new alliances would have to be formed to survive. It could also explore how the characters would change in this new situation.
Another plot could involve a group of pilots from different nations coming together to fight a common, mysterious enemy force that doesn't belong to any known country. Their different flying styles and cultures clash at first but they learn to work together for the greater good.
One popular ace whitebeard fanfiction might be those that explore their relationship as a father - son like bond. In many of these stories, Ace's growth under Whitebeard's protection and guidance is depicted. For example, there could be a story where Ace overcomes his inner demons with Whitebeard's encouragement.