There are no such inappropriate 'Straight Shota' stories in the official Dragon Ball Z canon. Dragon Ball Z mainly focuses on epic battles, power-ups, and the adventures of Goku and his friends to protect the Earth from various villains.
The story of Dragon Ball Z Kai follows Goku and his friends as they defend the Earth from various powerful threats. It includes battles against villains like Frieza, Cell, and Majin Buu. Goku, a Saiyan, constantly trains to become stronger and uses his martial arts skills and special abilities like the Kamehameha wave.
Dragon Ball Z is both anime and manga. The anime was adapted from the manga and they share the same story and characters, but presented in different mediums.
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.
A Kryptonian in the Dragon Ball Z universe could potentially be a very powerful addition. Their natural abilities like super strength, flight, and heat vision could make them a force to be reckoned with. However, they would also face challenges as the Dragon Ball Z world has its own power scale with ki-based powers. They might have to adapt to the different fighting styles and power sources. Maybe they could learn to use ki in addition to their Kryptonian powers, or they could find a way to combine the two in unique ways.
The main characters are Goku, a Saiyan who is the hero of the story. Vegeta, another Saiyan who starts as an enemy but later becomes an ally. Gohan, Goku's son. Piccolo, a Namekian. Krillin, Goku's best friend. And Bulma, who is important for inventing things that help the characters in their battles.
One interesting Dragon Ball Z Kai fan fic could be one that focuses on an alternate timeline where Goku never hit his head as a baby. This would change his personality and the entire course of the story. Another could be a story centered around Vegeta's training in a new, uncharted planet, exploring his growth without the constant presence of Goku. There are also fan fics that might explore the backstories of minor characters like Yamcha or Krillin in more depth, which can be really fascinating.