His character can become more assertive. As a Saiyan in fanfiction, Gohan may no longer hold back his power or his opinions. He could be more vocal about his goals and desires, rather than being the quiet and reserved character we often see in the original story.
One trait is his love for combat. Goku would constantly seek out strong opponents to test his skills. Another is his Saiyan pride. He might not back down from a challenge even if it seems impossible. Also, his Saiyan appetite. He would probably eat huge amounts of food to fuel his Saiyan - level energy.
In fanfiction, Gohan acting like a Saiyan can bring out his latent Saiyan pride. He could start to flaunt his power more, not in an arrogant way but as a way to show that he is a true Saiyan. He may also start to embrace Saiyan traditions that he previously ignored, such as the Saiyan love for a good fight and the sense of honor in combat.
Well, it might make his relationships more intense. His Saiyan nature often means he's more aggressive and competitive. So, his friends like Krillin might be a bit more cautious around him. And his enemies would feel even more threatened. It could also lead to some friction with Vegeta as they both have Saiyan pride and might butt heads more often.
In the 'Gohan acts like Vegeta' fanfiction, a really interesting plot point is how Gohan deals with his family while in this new persona. Chi - Chi's reaction to his Vegeta - like behavior would be a major part of the story. Also, Gohan's newfound confidence might lead him to take on enemies he previously thought were too strong. And his interactions with the Z - Fighters, especially those who have a history with Vegeta, would be full of drama and tension.
The theme of self - discovery is often present. The female Saiyan may be trying to figure out her place in the universe, and Gohan, with his own experiences, helps her. Or Gohan himself might be on a journey of self - discovery with the female Saiyan as a catalyst, especially in terms of his Saiyan heritage.
Caulifla could be a great choice. She's strong - willed and has a passion for fighting. Her energetic personality could create an interesting dynamic with Gohan, who is more reserved in some ways.
Well, if Gohan starts acting like Vegeta, it might strain his relationship with Piccolo at first. Piccolo is used to the more mild - mannered Gohan. But over time, Piccolo might come to respect this new assertive side of Gohan. With his father Goku, Gohan's new Vegeta - like behavior could create some friendly rivalry. Goku might be a bit surprised but also excited to see this new side of his son.
One idea could be Gohan in his Super Saiyan 4 form facing a new, powerful enemy from another dimension. He could struggle at first to control the raw power of this form while also trying to protect his friends and family. Maybe this new enemy has the ability to nullify the Saiyan's energy attacks, forcing Gohan to rely more on his martial arts skills that he learned from Piccolo.
In some fanfictions, an OC Saiyan could be a time - traveler who meets Gohan at different points in his life. This OC Saiyan could change the course of Gohan's life in small ways, like helping him to train harder during his childhood or giving him advice during the Cell Games that he didn't receive in the original story. This would create a whole new timeline of events for Gohan and the Dragon Ball universe.