So recently I've read a story about 3 friends reincarnating together into the world of MHA with the powers of Madara Uchiha, Obito Uchiha and Itachi Uchiha. This idea was inspired by it.
Fanfiction: The Uchiha's in MHA (This is the fanfiction that inspired this idea.)
...
3 friends/bothers die in a car accident and end up meeting god who lets them reincarnate into the world of One Piece as Ace, Sabo and Luffy.
(Make them reincarnate around the time when Luffy and Ace met Sabo for the first time.)
Unlike in the original where they all go their own ways, they decide to stick together while also gathering the other characters such as Zoro, Nami, Ussop, Masked Deuce etc...
You can have one of the 3 as the MC while other are secondary characters like what Sasuke is in Naruto.
The most important part about this fanfiction is the the banter/dialogue between the 3 MCs.
It would also be cool if they were also similar in personality as to the characters they took over but obviously smarter and with future knowledge.
With future knowledge they also become way more powerful compared to canon (obviously)
You could also lock away some of their knowledge so they dont become cheat codes which they will anyways 😂