A third storyline could be about the high school students discovering the Dragon Balls. They might start off thinking they're just some cool artifacts, not realizing their true power. As they start to figure it out, they could get into all sorts of adventures, with the Z - fighters having to step in to protect them from those who would misuse the Dragon Balls.
Vegeta is also popular. His prideful and brooding nature would be really interesting in a high school environment. He might be the loner who's secretly really powerful and has a soft spot for a certain girl at school.
One possible plot could be that the characters from Dragon Ball Z end up in the High School DxD world and have to deal with the different power dynamics and social hierarchies there. For example, Goku could be intrigued by the way the devils and angels in High School DxD have their own unique powers and politics. He might try to learn from them while also showing off his Saiyan strength.
A possible storyline is the characters forming a high school club related to martial arts or self - defense. They could teach other students and at the same time learn more about human relationships and teamwork. This would be a great way to see how they adapt to normal high school life while still having their unique powers and abilities.
Goku is often very popular. His naivete and pure heart would make for some interesting high school scenarios. He'd probably be the friendly jock type who is always eager to help out.
One alternative is to focus on character backstories. You could write about the early days of Piccolo, how he came to be the way he is. Another option is to do crossovers with other non - sexual universes. Maybe a story where the Dragon Ball Z characters meet characters from a magical anime world and they have to work together to solve a problem. Also, you can write about the relationships between the characters in a platonic way, like the deepening of the friendship between Gohan and Krillin.
Some 'Dragon Ball Z Fanfic' worth checking out are 'The Lost Saiyan'. This fic tells the story of a Saiyan who was lost in space and finally makes his way to Earth. 'Piccolo's Secret Training' is another one. Here, Piccolo undertakes a training that could change the balance of power. And 'The Dragon Ball Hunt' is an exciting fanfic where characters are on a quest to find all the Dragon Balls for a very different reason than in the original.
Many Dragon Ball Z Cell fanfics might explore alternate timelines. For example, what if Cell had successfully absorbed all the Androids before facing Goku? This would have made him even more powerful and could have led to a completely different outcome for the Dragon Ball Z universe. It's exciting to think about all these different possibilities.
First, familiarize yourself with the Dragon Ball Z world, its characters, and their personalities. Then, come up with an engaging story that fits within that framework. Pay attention to the action sequences and power levels to keep it consistent with the series.
Goku would be really interesting. His pure - hearted and naive nature would contrast greatly with the more complex and often morally ambiguous characters in High School DxD. He would see the battles and power struggles in a different light, probably just wanting to test his strength and have a good fight without getting too involved in the politics.