Frieza might initially be shocked. He's used to being a feared and powerful being, and the idea of having a family is very foreign to him. So he could be in denial at first.
Some writers show the Frieza race's culture as being very hierarchical. There's a clear pecking order, with the strong ruling over the weak. They might also depict their culture as being focused on power acquisition. For example, in many fanfictions, young Frieza race members are trained from a young age to be powerful warriors.
Frieza's back story is complex. He rules over a vast intergalactic empire. He's not just powerful physically but also very intelligent when it comes to ruling and conquering. He is often seen as a symbol of pure evil in the Dragon Ball universe. His back story involves his early days of learning about power and how to use it to his advantage. He starts small with his conquests and gradually builds his empire. His relationship with his subordinates is also based on fear. He will not tolerate any form of disobedience, and his wrath is something that everyone in his organization fears.
The key elements include his position as the leader of the Planet Trade Organization. This gives him the means to carry out his conquests. His inborn strength is also a big part of it. He uses his power to subjugate others. Also, his discovery of the Saiyan threat and his attempts to eliminate it are crucial in his back story.
For Yamcha, you can focus on his growth from being a bit of a comical character to a more serious and respected fighter in the context of his relationship with Frieza. Maybe he learns from Frieza's cold and calculating nature how to better strategize in battles. For Frieza, his development could be about him learning to care for someone other than himself. He could start to see Yamcha as an equal, which is a huge shift from his usual superiority complex.
Naruto's love for his friends and his village would translate into a new form in this rebirth. He might see the people in the Dragon Ball universe as his new family and friends. His outgoing and friendly nature could start to break down the walls of fear that Frieza had created. He would be less likely to immediately resort to violence like the old Frieza, instead trying to talk things out first, but still be ready to fight if necessary to protect those he cares about.
If Naruto were in Frieza's body in fanfiction, it could lead to some interesting power dynamics. Naruto is used to his own set of chakra - based powers, but now he has Frieza's immense strength. He would probably struggle at first to control Frieza's body and its abilities. However, his indomitable spirit would likely drive him to master it quickly. He could then use Frieza's reputation to his advantage, perhaps surprising his enemies in the Dragon Ball world who expect the same old evil Frieza.
Well, it could be that in the fanfic, Bardock's group forms an unexpected alliance. Perhaps they team up with another powerful race or a group that has some sort of technology or magic that can counter Frieza. This alliance provides them with the means to not only fend off Frieza but also to ensure their survival. Another possibility is that there is some sort of time - travel or dimension - hopping involved. They could escape to a different time or dimension where Frieza can't reach them.
Then, introduce some shared experiences. Maybe they get trapped in a strange dimension together. In this new and dangerous place, they have to rely on each other's strengths. Goku's physical power and Frieza's cunning could be the keys to their survival. As they go through these experiences, they start to see each other in a new light and their relationship begins to change.
Yes, there are likely 'Bardock Kills Frieza' fanfics out there. The Dragon Ball universe has a huge fan base, and many fans like to create alternative storylines. You can try searching on fanfic websites like FanFiction.net or Archive of Our Own.