Another plot could be that Goku goes back to his childhood days in the mountains with Grandpa Gohan. He could relive those simple days but also use his current knowledge and power to protect Grandpa Gohan from any threats that he might not have been able to handle before.
Maybe Goku goes back to the time when Planet Vegeta was still intact. He could try to prevent Frieza from destroying it. This would change the entire Saiyan race's fate and might create a whole new timeline with a powerful Saiyan empire.
Well, perhaps Goku travels back in time to meet his long - dead parents. He could have conversations with them, learn about his family's history in a more personal way, and gain new insights that help him in his present - day battles. Or he might go back to the time when the Saiyans were still on their home planet, and try to change the fate of the Saiyan race by warning them about their impending doom.
One idea could be that Goku and Vegeta travel back in time to the Saiyan - Planet. They could try to change the fate of the Saiyans, like preventing Frieza from destroying their planet. This would bring a whole new set of challenges as they would have to deal with the Saiyan culture and politics of that time.
One idea could be that Goku and Goku Black are forced to team up against an even greater threat from another universe. They start to understand each other's fighting styles during the battle and gradually develop a grudging respect for one another.
In some versions, the female Goku could be part of a prophecy. The two Gokus meet, and at first, there is some confusion and misunderstanding. But as they get to know each other, they discover that they are key to fulfilling the prophecy. They combine their powers and defeat an ancient evil that was threatening both of their worlds.
One idea could be that Percy and Artemis are sent back to the time of the Titans' rule. They have to work together secretly to gather allies among the minor gods and demigods who are oppressed. Another could be they go back to the founding of Camp Half - Blood and have to make sure the important events occur as they should while also dealing with a threat that could change the future of the camp. A third plot idea might be that they are thrown back to a time when a powerful artifact was first created, and they need to prevent it from falling into the wrong hands to safeguard the future of the demigod world.
One idea could be a story where Bulma creates a new device that accidentally sends Goku and her to a parallel universe. There, they have to work together to find a way back home while facing new and strange enemies. Another could be a time - travel plot where they go back in time to before Goku met Chi - Chi and Bulma realizes she has feelings for him. The third idea is a story where Goku and Bulma get trapped on a deserted planet and must rely on each other's skills to survive and escape.
One idea could be a crossover universe where Goku somehow ends up in the Naruto world and meets Sakura. They could team up to fight a new common enemy that is causing chaos in both their worlds. Maybe this enemy has the ability to steal energy like the Saiyans but also uses genjutsu like the ninjas.
One plot idea could be that Baby takes over Goku's body and tries to use his power to conquer the universe in a more subtle way. He might pretend to be Goku at first and manipulate his friends into doing his bidding without realizing it.
Maybe there could be a story where Android 18 gets sent to a different dimension and Goku and Vegeta have to follow her to bring her back. In this dimension, the rules of power and fighting are different. They all have to adapt quickly. Goku and Vegeta might learn some new skills from Android 18 as she has a different way of approaching combat situations due to her android nature.
One idea could be Goku traveling back in time to train with his past self. He could teach his younger self how to achieve the SSJ God form more quickly, which would change the power dynamics in his original timeline battles. For example, against Frieza, if he had the SSJ God power earlier, the fight would be much shorter and less arduous.