Perhaps Lime could be from a different planet and she comes to Earth seeking help. Gohan befriends her and they go on a journey to find a way to save her planet. Along the way, they encounter various challenges and also learn more about each other's cultures.
One idea could be Gohan and Lime teaming up to face a new and powerful enemy that neither of them could defeat alone. They could train together, with Gohan teaching Lime some of his Saiyan techniques.
One idea could be Goku and Gohan going on a special training journey to a new planet with unique gravity and energy sources. This would force them to adapt and develop new techniques together.
One idea could be Future Gohan training a new generation of fighters in a post - apocalyptic world. He could pass on his skills and knowledge, creating a new hope for the future. Another plot could involve him finding a way to travel back in time to prevent the events that led to his world's destruction. Maybe he discovers a hidden power within himself that he didn't know he had and uses it to fight against the remaining threats in his world.
Perhaps a story where Gohan and Videl have to team up to protect their family from a new and powerful threat that is specifically targeting them. They would have to use their combined skills and the power of their relationship to overcome it. In this fanfiction, we could see how their love for each other and their family gives them the strength to fight.
One idea could be Gohan crossing over into the Naruto universe. He could team up with Naruto and use his Saiyan powers to fight against the Akatsuki. Another plot could be Gohan in the Harry Potter world, using his ki to defend Hogwarts from Voldemort. Or perhaps Gohan in the DC universe, fighting alongside Superman against a common enemy.
One idea could be Gohan traveling back to the Saiyan - Planet Vegeta era. He could try to prevent the destruction of the Saiyans by Frieza. Maybe he'd use his knowledge of future events and his advanced power to stand up to Frieza earlier. Another plot could be him going back to a time during the Cell Games. He could train his past self more effectively, leading to an even stronger version of himself to face Cell.
A plot could revolve around Chichi wanting Gohan to focus more on his studies and less on training. This causes some tension between them as Gohan feels he needs to train to protect his family. It could show how they resolve this difference in priorities.
She could be kidnapped by an enemy who wants to use her as leverage against Gohan and the other Z - fighters. This would lead to a rescue mission where the Z - fighters have to face new and powerful foes. For instance, the kidnappers might be from a far - off planet that has a grudge against the Saiyans.
Maybe an evil scientist who has created a new form of bio - weaponry. He targets Gohan and Lime because they pose a threat to his plans of world domination. His creations could have abilities that are a challenge for Gohan and Lime to counter.
One interesting Dragon Ball Z Lime fanfic could be one that focuses on an alternate universe where Lime characters have unique powers. For example, a fanfic might explore a scenario where a Lime character has the ability to control time, which could lead to really cool battles and plot twists.
One idea could be Gohan in his Super Saiyan 4 form facing a new, powerful enemy from another dimension. He could struggle at first to control the raw power of this form while also trying to protect his friends and family. Maybe this new enemy has the ability to nullify the Saiyan's energy attacks, forcing Gohan to rely more on his martial arts skills that he learned from Piccolo.