Maybe Broly could be transported to a future timeline in a dbz broly crossover fanfiction. There, he meets the descendants of the Z - fighters. At first, they're wary of him, but Broly realizes he has a chance to change his reputation and helps them defend against a new threat that has emerged in that time.
One idea could be that Broly ends up in an alternate universe where he has to team up with Goku and the Z - fighters to fight a new, even more powerful enemy. This would force Broly to control his anger and work with his former foes.
A Broly crossover with the Naruto universe could be really cool. Picture Broly in the Hidden Leaf Village, his incredible power causing quite a stir. Maybe he could get involved in the fight against the Akatsuki, using his brute strength in a world of ninjas. It would be interesting to see how he adapts to chakra and ninja techniques.
One idea could be a crossover with the Dragon Ball Z heroes. Broly could team up with Goku and Vegeta to face a new, even more powerful enemy from another universe. This would bring out different fighting styles and power combinations.
One idea could be that Godlike Broly crosses over into the Dragon Ball Super universe and challenges Goku and Vegeta at their peak forms. His overwhelming power could force them to seek new power - ups and training methods.
A great plot for a Naruto DBZ crossover fanfiction might be that there is a rift in the multiverse which causes the two universes to collide. Naruto and his comrades are confused by the new power levels they see in the DBZ characters and vice versa. The Z - fighters are intrigued by the ninjutsu and different types of chakra. They decide to work together when they discover that an ancient evil, which was sealed away in both universes long ago, has been released due to the rift. The combined efforts of Naruto's Rasengan and Goku's Kamehameha could be a crucial element in their fight against this ultimate evil.
One idea could be that Ranma somehow gets transported to the DBZ universe. He could end up training with Goku and learn the Kamehameha wave, but with his own Ranma - style twist. Maybe he uses his martial arts skills from his world to create a new fighting style combined with ki. Another plot could involve the Dragon Balls. Ranma might accidentally make a wish on them that gets him involved in a big battle against a powerful villain in the DBZ world.
One plot idea could be that the Dragon Balls are accidentally brought into the Evangelion universe. This causes a stir as different factions in the Evangelion world, like NERV and SEELE, try to get their hands on them for their own purposes. Meanwhile, the Z - Fighters follow the Dragon Balls and end up in this strange new world. Another idea is that an Eva unit gains the ability to use ki, like a Saiyan. This Eva then goes rogue and starts causing chaos, and it's up to both the Evangelion pilots and the Z - Fighters to stop it.
For a 'dbz gohan crossover fanfiction', a plot where Gohan crosses into the DC Comics universe would be exciting. He could team up with Superman and learn about different types of powers. Maybe he'd help Superman understand the concept of ki. Another idea is a crossover with the Final Fantasy series. Gohan could find himself in a world full of summons and magic, and use his martial arts to fight alongside the Final Fantasy characters.
One idea could be that Broly is transported to an alternate universe where he teams up with Goku from a different timeline to fight a new, powerful enemy. They have to combine their unique fighting styles to stand a chance.
Vegeta could also be an interesting choice. Vegeta has his own pride and issues with power, much like Broly. In a crossover fanfiction, they could start off as rivals, constantly trying to outdo each other in terms of strength. But as the story progresses, they might find common ground and have to work together against a common enemy. This would be a great way to explore both of their characters in more depth.
A plot could involve a powerful villain who uses the concept of the harem to manipulate Naruto and Goku. The villain might create illusions or put the female characters in danger, forcing our heroes to work together. They would need to not only defeat the villain but also figure out their feelings for the harem members in the process. For example, Naruto's determination and Goku's strength could be combined in unique ways to face these challenges.