One way to develop their characters is to put them in situations that force them to grow. For example, if they were stranded on a hostile planet. Bardock would have to rely on his wits and not just his strength. Fasha could show her nurturing side, taking care of Bardock when he's injured. This would show different aspects of their personalities and help in their character development.
One idea could be exploring their relationship before Bardock was sent on his final mission. Maybe a story about them training together and sharing their dreams for the future of the Saiyan race.
They could go through a period of misunderstanding. Maybe Gohan makes a decision about his future that Chichi doesn't initially understand. Through communication and some trials, they grow closer as they learn more about each other's perspectives.
They could also develop their relationship through training. If Vegeta takes a more hands - on approach to training Trunks, not just as a student but as his son, they could bond over the shared experience of pushing their limits. They could learn new techniques together and grow closer as a result.
One great Bardock in Dragon Ball Z fanfiction is often depicted as a fearless and noble Saiyan. He is shown as a warrior who, despite the cruel nature of the Saiyan race at that time, had a sense of honor. In some fanfictions, he manages to break free from the control of Frieza in more creative ways than in the original story, making his character even more complex and interesting.
For Cabba, his character could be developed by showing more of his insecurities. Maybe he doubts his ability to lead his people compared to the great Saiyan warriors he has heard about. Caulifla, on the other hand, could be developed by exploring her softer side. Usually she is all about fighting, but showing her caring for her friends or family in a fanfiction would add depth.
One way to develop both characters is by putting them in a situation where they have to rely on their wits rather than just their strength. For example, they get trapped in a high - tech prison designed by an enemy. They have to figure out how to escape using their intelligence and the limited resources around them. This would force them to grow in ways that they haven't before and show different aspects of their personalities.
A popular version of Bardock in fanfiction is the one who has a premonition of the destruction of the Saiyans much earlier. This Bardock then tries to take actions to prevent it, like gathering other Saiyans who might be sympathetic to his cause. It makes him a hero figure right from the start, rather than just a victim of Frieza's wrath as in the original story.
A fanfiction might explore the idea of Bardock seeing Goku's life through a time - space rift. He witnesses all of Goku's battles and the friends he makes. Bardock is filled with pride but also realizes that Goku has a different path than the traditional Saiyan way. This makes him question the Saiyan culture he once knew. Meanwhile, Goku starts to have strange dreams about his father, which leads him to search for more about his Saiyan heritage.
Obviously, Bardock himself. And of course, Goku would likely be in it since he's Bardock's son. Vegeta might also show up, as he is an important Saiyan character. There could also be other Saiyans like Nappa or Raditz, especially if the story is about Bardock trying to reform or reunite the Saiyan race.
Goku is a great character to pair with Bardock. Since Goku is his son, it can create some really emotional and action - packed scenes. They can train together or fight side by side against common enemies. Another good option is Vegeta. Their different personalities as Saiyans can lead to interesting interactions. Bardock's old - school Saiyan ways compared to Vegeta's pride can make for some engaging storylines.