A possible plot in this fanfiction could be a tournament - style story. A powerful being creates a tournament that combines the worlds of Naruto and Dragon Ball Z. The prize is a wish that could change the fates of both universes. Naruto and Goku enter the tournament, and their harems support them. The harems could also have their own mini - adventures and rivalries within the tournament setting. Maybe some members of the harems start to learn new skills from each other, like a kunoichi learning how to use ki or a Saiyan learning some ninja techniques.
Well, a cool plot might be that the Sage of Six Paths in Naruto has a connection to the Kais in Dragon Ball Z. This connection leads to a situation where Naruto and Goku have to work together to stop an ancient evil that threatens both universes. For example, the evil could be a powerful demon that feeds on both chakra and ki. They would have to combine their powers and the powers of their friends to stand a chance. Naruto could teach Goku some of his shadow clone jutsu, and Goku could show Naruto how to achieve Super Saiyan forms.
A great fanfiction idea could be about the Dragon Balls being accidentally transported to the Naruto universe. This would cause chaos as various ninja clans try to get their hands on them for different reasons. Maybe Naruto himself would be the one to discover them first and he has to figure out how to use them or protect them from those with malicious intent. And of course, there could be some fun interactions between Naruto's friends and the Dragon Ball Z characters who come looking for the balls.
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.
One interesting plot could be a new villain emerging from a long - forgotten dimension. This villain has powers that are a mix of different techniques from all the universes in Dragon Ball. He starts causing chaos by stealing the energy of strong fighters to open a portal to an even more powerful realm.
Another interesting plot could be that the gamer aspect brings in virtual reality elements. The Z - fighters enter a virtual world where they have to fight enemies with different rules. This virtual world could have power - ups and obstacles that are based on video game concepts, like finding hidden keys to unlock new areas or defeating bosses to gain special abilities that they can then use in the real Dragon Ball Z world.
One idea could be a crossover with the Naruto universe. Goku and Naruto could team up to fight a common enemy. Maybe they face an evil villain who has the power - stealing abilities like Cell and the ability to use powerful ninja jutsus. Another plot could be a crossover with One Piece, where Luffy and Goku have a friendly competition about who can eat more food and then end up having to work together to defeat a new threat at sea that has the strength of Saiyans and the deviousness of pirates.
Perhaps a fanfiction where a young Saiyan from a destroyed planet manages to find their way to the Xenoverse 2 world. This Saiyan has a different fighting style compared to the ones we know. They join the Time Patrol not just to save timelines but also to find a new home for their kind. Along the way, they face discrimination from some of the other races in the Xenoverse due to their Saiyan heritage, but they prove themselves worthy through their strength and determination.
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.
One idea could be that after the defeat of a powerful enemy, Goku accidentally ends up in a parallel dimension where he meets multiple female characters from different eras of Dragon Ball. They all develop feelings for him due to his heroic nature. Another plot could be that Vegeta, in an attempt to outdo Goku, gets involved in a situation where he has a harem of his own, but he's constantly struggling to understand their emotions as he's so focused on training. A third idea is that a new female Saiyan arrives on Earth and she has a special power that attracts many of the male Dragon Ball characters, leading to a complex web of relationships and a harem - like situation.
One idea could be that Female Vegeta and Goku are forced to team up for a special mission. They start off bickering as they usually do, but as they face challenges together, they begin to respect each other's fighting styles more. Maybe they have to battle a new, extremely powerful enemy that neither could defeat alone. This situation could lead to some interesting character development and a budding friendship or something more.