Perhaps a fanfiction where Vados senses a new threat approaching the universe. She enlists Goku to help her find a way to stop it. Along the way, they encounter strange new races and powers. Goku's simple but powerful approach to fighting combined with Vados' wisdom would make for an interesting dynamic as they search for a solution to this impending doom.
Goku's understanding of different universes and races could be deepened in fanfiction. Since Dragon Ball Super introduced the multiverse concept, fanfiction could explore how Goku interacts with and learns from beings from other universes, making him more worldly and less naive in some ways.
It's really hard to say. Goku has his Super Saiyan forms which give him incredible power boosts. But Superman has super strength, heat vision, and is nearly invulnerable. In a short fight, Superman might have the edge due to his instant powers like flight and super strength without having to power up. But if Goku manages to reach his higher Super Saiyan forms and uses techniques like the Spirit Bomb, he could potentially defeat Superman.
I think Saitama is stronger. His power is seemingly limitless and he has never struggled in a fight. Goku, although powerful, has had many intense battles where he was pushed to his limits.
One of the interesting power - ups could be his Ultra Instinct form. In fanfiction, it might be further enhanced, like having different levels that are not shown in the original. For example, he could have an Ultra Instinct - Kaioken combination which would be extremely powerful.
Goku and Bulma have many exciting adventures. They first set out to find the Dragon Balls together. Along the way, they encounter various foes and challenges. Bulma provides the technological know - how, like using her Dragon Radar to locate the balls, while Goku uses his martial arts skills to protect them from danger.
In a sense, it could also be normal if we consider that Goku is always open to new experiences. He has been exposed to different planets, cultures, and types of power in his own story. So, watching a fan - created version of his story, although different, could just be another new thing for him to experience, even if it seems a bit strange at first.
Caulifla and Goku's relationship in fanfiction could be really interesting. Maybe in this fanfiction, they start as rivals. Caulifla, with her Saiyan pride, wants to prove she's stronger than Goku. But as they fight more, they begin to understand each other's fighting styles and develop a mutual respect. This could lead to some really cool training sessions where they both learn new techniques from one another.
A fanfiction might explore the idea of Bardock seeing Goku's life through a time - space rift. He witnesses all of Goku's battles and the friends he makes. Bardock is filled with pride but also realizes that Goku has a different path than the traditional Saiyan way. This makes him question the Saiyan culture he once knew. Meanwhile, Goku starts to have strange dreams about his father, which leads him to search for more about his Saiyan heritage.
One possible fanfic could be about Bulma and Young Goku's first adventure together. It might start with Bulma recruiting Goku to find the Dragon Balls. They could face various challenges like wild animals and bad guys along the way. Their different personalities, with Bulma being smart and resourceful and Goku being naive but strong, would create interesting interactions.