Vegeta could also be an interesting choice. Vegeta has his own pride and issues with power, much like Broly. In a crossover fanfiction, they could start off as rivals, constantly trying to outdo each other in terms of strength. But as the story progresses, they might find common ground and have to work together against a common enemy. This would be a great way to explore both of their characters in more depth.
One common theme is power and its control. Since Broly is known for her extreme power in the original series, in the fanfictions with a female Broly, a lot of stories focus on how she manages this power, especially in a world dominated by male Saiyans. Another theme is identity. As a female in a male - centric universe, she often has to find her place and prove herself.
In a Broly - losing - control scenario in a DBZ reader insert fanfic, the story might focus on how the reader's actions affect the outcome. For example, if the reader is a Saiyan as well, they could try to communicate with Broly on a level that other characters can't. They might understand his pain of being an outcast and use that connection to stop his rampage. It could also be that the reader has some knowledge from the future or another dimension that gives them an edge in dealing with Broly.
One popular 'dbz broly x trunks fanfic' is 'The Unlikely Bond'. It explores an interesting dynamic between them as they face a new threat together in a creative storyline.
Another theme is redemption. Given her potentially villainous nature in the original, many fanfics give her a path to redemption. This could involve her making amends with characters she has wronged in the past. It often involves her learning about friendship and loyalty along the way. For instance, she might start off as a loner but gradually form bonds with other Z - fighters.
A really interesting plot could be that Broly trains Gohan in a parallel dimension where the rules of power are different. Gohan has to learn to adapt to this new environment while also dealing with Broly's tough training. This could lead to some really cool power - up moments for Gohan.
Well, the plot might involve Broly somehow getting stranded on Earth where Gohan lives. Gohan, being the kind - hearted Saiyan - human hybrid, decides to help Broly adapt. In the process, they train together. Gohan tries to teach Broly about control, while Broly shows Gohan new levels of power. Their friendship grows and they end up protecting Earth from other threats that come their way.
In this 'dbz gohan snaps fanfiction', it may depict Gohan's transformation from his normal self to a more extreme state. This could be due to a variety of factors. It could be related to the constant battles and the toll it takes on his mental state. Or perhaps he discovers some dark secret that makes him snap. The fanfiction would likely detail his internal struggle, his newfound abilities if any, and how it impacts the overall Dragon Ball Z universe. His friends and foes would surely be affected by this change in Gohan, and the story could explore all these aspects in great detail.
Goku is often a common character. Since Gohan has a strong relationship with his father, in time - travel scenarios, they might interact a lot. For example, Gohan could go back in time to save Goku from an early death or to train with him. Vegeta is also a likely character. He might be skeptical of Gohan's time - traveling at first but then get involved in Gohan's plans. Another common character would be Piccolo. He has been Gohan's mentor, and in time - travel stories, he could offer his wisdom and help to Gohan again.
One common theme is the discovery of the other. Broly is often depicted as a complex and misunderstood character, so in these fanfics, the reader gets to discover his true self. And Broly also discovers the unique qualities of the reader.