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.
One idea could be to have Cooler return with a new, even more powerful form. He could be seeking revenge against Goku for past defeats. Maybe he's allied himself with a new, mysterious villain from another part of the universe. He arrives on Earth with his newfound power and allies, ready to take on Goku and the Z - fighters in an epic battle that shakes the very foundations of the planet.
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 Dragon Ball cooler fanfiction could be about a new Saiyan form that is discovered. Maybe it's a form that combines the power of Super Saiyan with the coolness of the Yardratian techniques. In this fanfiction, Goku or another Saiyan character could learn this form from an ancient scroll or a mysterious alien.
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 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 a fanfic where Goku discovers a new form that is a combination of Ultra Instinct and Super Saiyan God. This form gives him unique abilities and a new look. Another idea is to have Vegeta go on a solo adventure to a new planet filled with powerful foes that force him to develop a new fighting style. Maybe also a story where the Z - fighters have to team up with their old enemies like Frieza to fight a greater threat from another dimension.
One idea could be Trunks and Mai going on a time - traveling adventure together to prevent a new threat in an alternate timeline. They could use their combined skills and knowledge to outwit the enemy.
Maybe Raditz gets sent to an alternate universe in Dragon Ball Super. There, he meets different versions of the Z - fighters. He has to team up with them to fight a common enemy that is threatening both universes. This would allow for some cool battles and character development for Raditz as he learns from these new allies.
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.
One idea could be a tournament where characters from Dragon Ball and Smash Bros universes compete for a super powerful artifact. This would bring together the unique fighting styles of both, like Goku's Kamehameha against Mario's fireballs.