One idea could be Mihawk getting transported to a different part of the One Piece world where he has to team up with the Straw Hats to face a new and powerful enemy. Maybe a group of ancient sea gods that are awakened and threatening to destroy all pirates. The Straw Hats could initially be wary of Mihawk but soon realize his skills are crucial for their survival.
Another plot could involve Mihawk being cursed by a strange devil fruit user. As a result, he loses his sight completely but gains an enhanced sense of other abilities like hearing and smell. He then has to rely on his newfound senses and the help of a young pirate crew, which he reluctantly accepts, to find a way to break the curse. This could lead to some interesting character development for Mihawk as he adapts to his new situation.
For a dracule mihawk crossover fanfiction, a great plot could involve crossing over with the One Piece world but in an alternate timeline. Maybe Mihawk teams up with Luffy at a much earlier stage. They could face new and unknown pirates together. Also, a crossover with the Bleach universe. Mihawk could enter the Soul Society and his sword skills could be compared to the Zanpakuto abilities of the Soul Reapers. He might even engage in battles with some of the powerful captains.
A plot could revolve around Perona trying to cheer up Mihawk. Since he is often portrayed as a rather stoic and solitary figure. Perona could use her unique personality and ghostly antics to bring some unexpected humor and light into Mihawk's life. For example, she could create ghosts that re - enact funny scenes from Mihawk's past battles, which at first he is annoyed by but then starts to find amusing.
One idea could be that they team up to face a new, extremely powerful enemy that threatens the balance of the New World. This enemy could be a former Rocks Pirate member who was in hiding and now has a plan to take over. Shanks and Mihawk, despite their differences, realize they need to combine their skills.
Zoro would be an obvious choice. Since Zoro has always aspired to defeat Mihawk, a crossover could show them in a situation where they have to put aside their rivalry and fight together. It could be a great opportunity to explore their relationship further and how they might learn from each other in combat.
One idea could be Zoro seeking extra training from Mihawk in a secluded place. During this time, they start to understand each other's pasts and the reasons behind their swordsmanship. Another could be a scenario where they have to team up against a common enemy that threatens the world of swordsmen. This would force them to combine their skills and learn to trust one another on a deeper level.
One plot idea could be that they start off as rivals but then have to team up to face a common enemy. During their time together, they gradually come to understand and respect each other on a deeper level, leading to a change in their relationship.
Perhaps a villain from DBZ, like Frieza, finds a way to travel to the One Piece universe. He starts enslaving the pirates and taking over islands. Luffy and his crew would be the first to resist, but they quickly realize they need help. Goku and Vegeta then arrive and have to teach the pirates about ki and how to fight against Frieza's powerful minions. It would be a great opportunity to see the different fighting styles blend together.
A cool plot could involve the Pokemon world's Team Rocket equivalents trying to steal the One Piece. They might think it's some sort of ultimate Pokemon - related power source. Meanwhile, the Pokemon trainers in the One Piece world could form alliances with the pirates. For example, a water - type Pokemon trainer could team up with Sanji on a ship, using their Pokemon's water abilities to help with cooking and other ship - related tasks.
One idea could be that the Straw Hat crew somehow ends up in the world of RWBY. Luffy might be intrigued by the different fighting styles and semblances. For example, he could try to learn how to use aura. Another plot could involve Ruby Rose meeting Nami and being fascinated by her Clima - Tact skills. They could team up to fight a common enemy that threatens both their worlds.
A cool plot could be a powerful gamer who has the ability to control digital elements in the real world. They enter the One Piece universe and team up with the Straw Hats. They create digital fortresses and weapons for the crew during battles. Or perhaps a devil fruit in the One Piece world gives someone the power to enter and manipulate game worlds, and the story follows their adventures between the two realms.