One idea could be Goku and Gohan going on a special training journey to a new planet with unique gravity and energy sources. This would force them to adapt and develop new techniques together.
One idea could be Gohan and Lime teaming up to face a new and powerful enemy that neither of them could defeat alone. They could train together, with Gohan teaching Lime some of his Saiyan techniques.
One idea could be Future Gohan training a new generation of fighters in a post - apocalyptic world. He could pass on his skills and knowledge, creating a new hope for the future. Another plot could involve him finding a way to travel back in time to prevent the events that led to his world's destruction. Maybe he discovers a hidden power within himself that he didn't know he had and uses it to fight against the remaining threats in his world.
Perhaps a story where Gohan and Videl have to team up to protect their family from a new and powerful threat that is specifically targeting them. They would have to use their combined skills and the power of their relationship to overcome it. In this fanfiction, we could see how their love for each other and their family gives them the strength to fight.
One idea could be Gohan crossing over into the Naruto universe. He could team up with Naruto and use his Saiyan powers to fight against the Akatsuki. Another plot could be Gohan in the Harry Potter world, using his ki to defend Hogwarts from Voldemort. Or perhaps Gohan in the DC universe, fighting alongside Superman against a common enemy.
One idea could be Goku Jr facing a new, powerful enemy that has a unique power related to time manipulation. This would force him to train in ways he never has before and seek help from unexpected allies, like some of the older, wiser characters from the original Dragon Ball Z series.
A plot could involve Bulma creating a new device that Goku needs to use in order to defeat an extremely powerful enemy. Goku has to learn how to operate this device with Bulma's guidance, and they face many obstacles along the way. This would show their cooperation and how their different skillsets complement each other. It could also lead to some comical moments as Goku tries to understand the complex technology. Another interesting plot could be that they are both transported to an alternate dimension where the rules of the Dragon Ball world are slightly different. They have to figure out how to adapt and find a way back home while also uncovering the secrets of this new dimension.
Perhaps a fanfiction where Vegeta and Goku get transported to an alternate universe. In this universe, their roles are reversed, and they have to adapt to the new situation while still trying to find a way back home. They would face challenges that are unique to this new world and learn from each other in different ways.
One interesting plot idea could be that Frieza somehow manages to gain new powers on a distant planet and returns to challenge Goku again. But this time, instead of just brute strength, he uses cunning strategies. Another could be a scenario where Goku and Frieza are forced to team up against an even greater threat from another universe. This would be a great chance to explore their complex relationship.
One interesting plot idea could be Goku training Caulifla in a new form of Ultra Instinct. This would allow for a deep exploration of their mentor - mentee relationship. Caulifla is already a strong fighter, but with Goku's guidance, she could reach new heights. Another plot could involve them teaming up against a powerful new enemy that neither could defeat alone. They'd have to combine their unique fighting styles and powers to win.
One idea could be Gohan traveling back to the Saiyan - Planet Vegeta era. He could try to prevent the destruction of the Saiyans by Frieza. Maybe he'd use his knowledge of future events and his advanced power to stand up to Frieza earlier. Another plot could be him going back to a time during the Cell Games. He could train his past self more effectively, leading to an even stronger version of himself to face Cell.