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.
They could interact through training sessions. For example, Goku could teach some of the Naruto characters how to better control their energy, similar to ki control. In return, Naruto characters could show Goku and others some of their unique jutsu. In a harem setting, the female characters from both sides could be observing and learning as well, which would create interesting interactions and potential relationships.
Another aspect to consider is how the Super Saiyan transformation would affect the relationships in the Naruto world. If Sasuke were to gain Super Saiyan powers, it could either drive him further away from Naruto due to the newfound power or bring them closer as they explore the new abilities together. Also, the concept of ki from Dragon Ball and chakra in Naruto could be merged, creating a whole new type of energy for the characters to utilize.
A Super Saiyan in Naruto fanfiction could be a result of a dimensional rift. Maybe a portal opens between the Naruto and Dragon Ball universes and some Saiyan energy seeps through, affecting a Naruto character. This would be an interesting plot device as it would introduce an alien concept to the ninja world.
Friendship is also a big theme. Even though it's a harem fanfiction, the bonds between characters from both series are explored. They might team up to face a common enemy or help each other out in personal matters. It's like how in the original shows, friendship was always important. In these fanfictions, it can be even more complex with the harem dynamic added.
In Naruto's harem, Tenten could be there. She's a skilled kunoichi. Ino might also be a part of it as she has interacted with Naruto quite a bit. From Dragon Ball Z, Chi - Chi could be in the mix. Despite being Goku's wife, in this fanfiction concept, she could be interested in Naruto too. Videl could also be part of the harem. She has a strong personality like Naruto and could be drawn to him.
Cultural clash is another common theme. The ninja world of Naruto and the more sci - fi/fantasy world of Dragon Ball Z have different values and ways of life. In these fanfictions, the fem Naruto has to bridge that gap. For instance, the way she approaches battles or how she views honor can be very different from the Dragon Ball Z characters, and this creates interesting storylines as they all interact in the harem environment.
Well, it depends on how you define fanfiction. Technically, Dragon Ball Super is an official continuation of the Dragon Ball series. However, it does have elements that feel like fanfiction. For example, some of the power - levels and new forms introduced seem a bit outlandish and more like what a passionate fan might come up with rather than a strictly logical progression from the original story. But it's still an official part of the franchise so it's a bit of a gray area.
A cool fanfiction concept would be a tournament where characters from both Dragon Ball Super and Naruto universes participate. It would be exciting to see how Naruto's clones would fare against Goku's Instant Transmission or Vegeta's Galick Gun.
One interesting crossover could be a battle between Naruto's Rasengan and Goku's Kamehameha. It would be epic to see the different energy forms collide. Maybe Naruto could learn some of Goku's training techniques and vice versa, like Naruto trying to achieve Super Saiyan levels of power or Goku learning about chakra control.