A fun plot might be a tournament - style story where the Super Trio enters a secret, intergalactic martial arts tournament. They face off against strange and powerful opponents from all over the universe. There are challenges not just in the fights but also in the rules of the tournament, which are different from the ones they are used to in the regular Dragon Ball tournaments.
One idea could be a time - traveling adventure. The Super Trio (let's say Goku, Vegeta and Gohan) get sent to a different era in the Dragon Ball universe, like the age of the Saiyans' home planet. They have to deal with the primitive Saiyan culture while also trying to find a way back home.
Another plot could be centered around a new powerful enemy that only the combined powers of the Super Trio can defeat. This enemy could have a unique power - stealing ability. As they fight, the trio has to learn to work together in new ways, with Goku's carefree attitude, Vegeta's pride, and Gohan's intellect all coming into play.
One idea could be a story where Goku and Vegeta from Dragon Ball Super end up in the world of Dragon Ball GT by some sort of time - space rift. They then have to team up with the GT versions of themselves to fight a new, powerful enemy that is threatening both timelines.
One interesting plot idea could be the return of an ancient and powerful villain from the Dragon Ball universe that was thought to be long forgotten. This villain could have powers that even the Gods of Destruction are wary of, forcing Goku and his friends to train in new and extreme ways.
A plot could involve Cooler getting trapped in an alternate dimension where the rules of power are different. He has to figure out how to adapt and escape while also facing off against strange new foes. Or perhaps he discovers a long - lost relative who has a connection to Earth, and this forces him to reevaluate his stance on the planet and its inhabitants.
A plot could revolve around a group of underdog fighters in Universe 2 who train in secret to enter the Tournament of Power. They face numerous challenges during their training, including a lack of resources and interference from more powerful groups. But through their determination and unique fighting styles, they manage to make a name for themselves in the tournament.
One idea could be creating a new character who has a unique power that challenges the existing power hierarchy in the Dragon Ball Super universe. For example, a character who can manipulate time in a different way than Whis or Beerus. Another plot could involve a tournament where fighters from different universes have to team up in unexpected combinations. This would lead to new rivalries and friendships. And perhaps a plot where the Dragon Balls are used in a completely different way, like to restore a destroyed universe but with some unforeseen consequences.
One idea could be that a character from Naruto's world somehow gets transported to the Dragon Ball Super universe and ends up in a harem situation. For example, Naruto himself could be sent there and due to his unique abilities and charm, attract the attention of various female characters like Bulma, Android 18, and Chi - Chi. Another plot could involve a new villain who uses the concept of a harem to manipulate characters from both universes, forcing them to work together to overcome this strange threat.
Well, a plot could be centered around Broly's origin. In this fanfiction crossover, it could be revealed that Broly has a connection to an ancient race in a different part of the Dragon Ball universe. Goku and Vegeta discover this and together with Broly, they embark on a journey to uncover the secrets of this race. Along the way, they face various challenges and battles, and Broly has to control his power better to help his new allies.
Perhaps a story where a previously unknown fighter enters the Tournament of Power. This fighter has been training in seclusion and has powers that are a combination of different techniques from various universes. They start off as an underdog but quickly become a force to be reckoned with, making allies and enemies along the way.
One idea could be that Goku from 'Dragon Ball Super' somehow ends up in a world full of lemon - like magical fruits that give him new powers. He has to learn to control these powers while also dealing with the strange inhabitants of this new world.
One idea could be a story where the Saiyan Blue form has an unexpected side effect. For example, it could start to drain the user's life force slowly but surely. Goku discovers this during a battle and has to find a way to either control it or reverse the effect while still fighting powerful foes.