Another plot could be that Goku's daughter has a natural ability to communicate with different species. This leads her on a journey across the galaxy to form alliances against a powerful alien race that plans to invade Earth. Along the way, she struggles with living up to her father's legacy and forging her own path.
Maybe a plot where Goku's daughter is kidnapped by an old enemy of Goku's who wants to use her to get revenge. She then has to break free and find her own power within to defeat this enemy. It could involve her learning about her father's past battles and using that knowledge to her advantage.
One interesting plot could be Goku's daughter having to train in a new dimension. She discovers unique powers there and has to use them to save the Earth from a new threat. This would be a great way to explore new aspects of the Dragon Ball Z universe while also focusing on a new character, Goku's daughter.
One interesting plot could be Goku and Bulma navigating the challenges of combining their very different lifestyles. Goku, being a Saiyan warrior, is used to constant training and battles, while Bulma is more into technology and inventing. In the fanfiction, they might struggle to find common ground in raising their family. For example, Goku might want to train their children in martial arts from a very young age, but Bulma could be more concerned about their academic education and safety. Another plot could be them facing threats from enemies who target their relationship. Maybe an old foe of Goku sees his marriage to Bulma as a weakness and tries to use it against him.
One interesting plot could be Goku traveling back in time to train with his younger self. He could teach his younger version some new techniques, like the Instant Transmission at an earlier stage. This would change the power dynamics in the earlier story arcs and lead to different battles against foes like Vegeta. Maybe the Z - Fighters would be stronger and better prepared for future threats.
One interesting plot could be Dark Goku's origin story. Maybe he's not just an evil version of Goku but has a more complex backstory involving some dark magic or a different dimension's influence. Another plot might involve his battles against the Z - fighters. How he uses his unique powers against them and the strategies they come up with to counter him.
In a fanfic, it could be that Android 21 has a hidden power that only Goku can unlock. As Goku helps her discover this power, they form a deep bond. This power could be related to the Dragon Balls in some way, like having the ability to control the Dragon Balls' wishes or even create new Dragon Balls.
A possible plotline could be that Bardock, in the afterlife, is able to communicate with Goku in his dreams. He warns Goku about an upcoming threat that is even more powerful than the villains he has faced so far. Goku then starts a new training regime in preparation for this threat, and along the way, he discovers more about his father's past and the true potential of the Saiyan race.
One interesting 'Dragon Ball Z Daughter Fanfiction' story could be about Goku's daughter who discovers a new power that even he doesn't know about. She has to learn to control it while facing off against new villains in the Dragon Ball universe.
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.
One interesting concept could be a female Goku having a different approach to training. Maybe she focuses more on finesse and speed rather than brute strength like the male Goku. She could also have a different relationship with the other Z - fighters. For example, her interactions with Vegeta might be less combative and more of a friendly rivalry.
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.
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.