Well, if Goku was the legendary Super Saiyan in fanfiction, it could completely change the power dynamics in the Dragon Ball universe. There might be new enemies or allies formed based on this twist.
If Goku were the legendary Super Saiyan in fanfic, it could lead to new story arcs and challenges. Maybe he'd face even more powerful villains or have to deal with the weight of his immense power.
In a crossover with One Piece, Luffy could be an ally. Luffy is known for his open - mindedness and ability to befriend almost anyone. He would see Broly's power and might try to get him to join his crew or at least fight alongside him against common enemies. They could have some really fun interactions, like Luffy trying to make Broly laugh or share his love for food with him.
In a crossover with the Naruto universe, Naruto himself could be an ally. Naruto has a way of seeing the good in people, and he might try to reach out to Broly and convince him to use his power for good. His ability to befriend and understand others could be key.