In the 'Bardock Saves Raditz' fanfic, perhaps Bardock discovers a way to time - travel. He goes back to the moment when Raditz is about to die. Bardock could use his own power to shield Raditz from Goku's Kamehameha. Then, they team up and start exploring other planets, trying to find a new place for the Saiyans to thrive, away from Frieza's tyranny.
One possible plot is that Bardock, who has somehow survived the destruction of Planet Vegeta, senses Raditz's life - force fading on Earth. He uses his remaining energy to teleport directly to Earth. Once there, he convinces Raditz to abandon his mission of getting Goku to join him in conquering other planets. They then join forces with the Z - Fighters against common enemies, like the Saiyans' old foes who might be planning to attack Earth after hearing about the Saiyans there.
Perhaps the main antagonist could be a new character. This new character could be an ancient evil that has been awakened by the presence of the Saiyans on Earth. They see Bardock and Raditz as a threat to their plans of taking over the universe and thus try to eliminate them.
It could be a story of redemption for Raditz. He starts off as a bit of a villain, but through interactions with Bardock (either as a memory or some kind of spirit guidance) and Goku's influence, he changes his ways. They could all be training together on Planet Vegeta before its destruction, with Bardock teaching them valuable Saiyan combat techniques and life lessons that shape them into the characters we know.
Bardock's power could be shown as more raw and instinctive. Since he was a pure - blooded Saiyan from a time when Saiyans were more about brute force and conquering. Raditz might have a power level that is in between Bardock and Goku. His power could be more focused on intimidation at first, but as the fanfic progresses, he could develop it further. Goku's power, on the other hand, would be more about growth and adaptability. He learns from his battles and constantly improves, so his power could be shown as evolving more rapidly than the others.
A possible plot twist could be that Bardock actually saves Broly, but in doing so, he unknowingly sets in motion a chain of events that leads to an even greater threat. For example, by saving Broly, he might disrupt the balance of power among the Saiyans in a way that angers some powerful factions, who then form an alliance with an external enemy.
One idea could be to focus on Bardock's perspective before his fateful battle. Maybe explore his thoughts about his son Goku being sent to Earth and his own impending doom. He could have some premonitions about Goku's future role in saving the universe.
One great 'Bardock Raditz Saga Earth Fanfic' could be about Bardock arriving on Earth earlier than expected. He might start to train some of the Earth's warriors secretly, changing the course of future battles. This would add an interesting twist to the Saiyan - Earth relationship.
I haven't read this particular fanfic directly, but generally, in a 'bardock saves broly' fanfic, it might involve Bardock using his combat skills and intuition. Bardock, being a Saiyan, has a certain level of power and tenacity. He could potentially save Broly from some sort of danger, like a powerful enemy or a life - threatening situation on their home planet. It could also explore the relationship between the two Saiyans, perhaps Bardock seeing potential in Broly or having a sense of kinship towards him.
One possible plot could be Bardock getting trapped in a Xenoverse where the rules of time and space are different. He has to find a way to get back to his own universe while facing off against powerful enemies.
One interesting 'Bardock Raditz Saga' fanfic could be one that delves deeper into Bardock's premonition powers. It might explore how he got them and what other visions he could have had. Another could focus on Raditz's early life on Planet Vegeta before being sent to Earth. There are also fanfics that might rewrite the saga with different outcomes, like Bardock surviving and changing the course of Saiyan history.
Well, it could be about Bardock somehow traveling through time to meet Gohan. Maybe Bardock wants to see the potential of his future grandson's power and they end up training together for a bit.