In some fanfictions, Goku and Raditz could form an unlikely alliance if they were faced with an even greater threat. For example, if a new and extremely powerful enemy emerged that threatened not just Earth but the entire Saiyan race. Raditz, who initially came to Earth with the intention of conquering it, might see the need to team up with Goku to save their home planet. Goku, being the good - hearted Saiyan he is, would be open to the idea if it meant protecting his loved ones.
Another scenario could be that Raditz is somehow brainwashed by a villain to be a good guy. Goku, sensing that Raditz is different, tries to reach out to him. They then find out that they have more in common than they thought. They both have a strong sense of Saiyan pride and a desire to prove themselves. This could lead to them working together to take on the real enemy behind Raditz's brainwashing.
If Raditz survived in fanfiction, he would likely have a complex relationship with Goku. He might start to see the value in Goku's way of life. Goku could try to reform him, and Raditz could slowly become a more positive force in the Dragon Ball Z universe.
If Raditz turned good, it would have added a whole new dynamic to the Dragon Ball Z universe. He could have become a valuable ally, sharing his knowledge and skills to help the heroes.
Well, one possible fanfic could be about Android 18 and Raditz teaming up against a common enemy. Maybe they initially start off as reluctant allies, but as they fight side by side, they begin to respect each other's strength.
One possible plot could be that Android 21, with her unique powers, teams up with Goku to face a new and powerful enemy. They might have to combine their strength and fighting techniques to defeat this foe.
In this kind of fanfiction, Goku might lose his family. For example, his friends and loved ones could be killed by a powerful new enemy. This would leave him in a state of deep despair and loneliness, and he would have to find a way to carry on without them.
He could die in battle. Maybe a new, extremely powerful villain emerges who has the ability to nullify Goku's powers or is just so strong that Goku's attacks have no effect. After a long and intense fight, Goku is defeated and dies.
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.
Perhaps in the fanfic, Android 18 uses her combat skills to train Raditz. Since she has a lot of fighting experience, she could help Raditz improve his techniques. This could lead to an interesting dynamic where Raditz becomes more powerful under her guidance.
One possible change is his power level. Fanfictions often give Goku new power - ups that are even more extreme than in the official story. For example, he could gain a 'Ultra - Ultra Saiyan' form that is many times stronger than the regular Super Saiyan forms. His appearance in this form could be very different, with longer hair, more defined muscles, and a new color to his aura. Another change could be in his family life. Maybe he spends more time with his family, teaching his sons and daughter new fighting techniques that he created himself. This would show a more domestic side of Goku that we don't see as much in the original series.
It would definitely change the dynamics of the story. Maybe their relationship would bring new challenges and opportunities for the characters.