Another scenario could be a love story between them. It would be a very unconventional relationship considering their different origins. Vegeta, a proud Saiyan, and Android 18, a powerful android. But perhaps in the fanfiction, they discover a deep connection. They might have to overcome many obstacles, like the disapproval of their friends and the differences in their very natures, but their love could prevail in the end.
One possibility is a story where Vegeta tries to train Android 18. He might see her potential and want to push her to become even stronger. This could lead to some interesting training sessions, with Vegeta's harsh Saiyan training methods clashing with Android 18's more laid - back attitude. However, in the end, she could become a stronger fighter under his guidance.
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.
A plot twist could be that Android 18 has some hidden Saiyan DNA. This would completely change the dynamic between her and Vegeta. They might then explore their newfound connection related to their Saiyan heritage together. Maybe she could even unlock some Saiyan - like powers, which would be a huge shock to everyone in the Dragon Ball Z universe.
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.
Maybe they could visit the Kai planet. Goku would be thrilled to meet the Kais again. He could learn new techniques from them. Vegeta might be jealous at first but then get interested in learning too. The other characters like Trunks and Goten could explore the beautiful landscapes of the Kai planet and have some friendly sparring matches with the Yardrats who live there.
They could team up to invent something amazing. Bulma has the brains and Gohan has the power and knowledge of the Saiyan abilities. Maybe they create a new type of energy shield that can protect the whole planet from any kind of attack.
Perhaps the fanfic could be a time - travel story. Android 21 accidentally sends Goku back in time to a point where she was first created. Goku then tries to prevent her from becoming the villain she was meant to be. This would involve Goku having to deal with the scientists who created her and convincing them to take a different path in their research, all while trying to find his way back to his own time.
It could also be a fanfic centered around their friendship. Android 18 might initially be cold towards Bulma, but as time goes on, they start to bond. Bulma could introduce Android 18 to the joys of normal life, like shopping or going to the beach. And Android 18 could protect Bulma from threats that her scientific work sometimes attracts. In the end, they become inseparable friends, changing the way the other characters view Android 18.
I really like 'Bulma and Vegeta: Partners in Adventure'. It's a fun fanfiction that has them going on all kinds of adventures together. It's full of action and also has some really sweet moments between the two. 'The Saiyan and the Scientist' is another great one. It explores how their different backgrounds - Vegeta being a Saiyan warrior and Bulma being a brilliant scientist - come together and create a really interesting dynamic in their relationship. And 'Vegeta's Soft Side for Bulma' is a great read as it shows the softer, more loving side of Vegeta that only Bulma gets to see.
There are fanfictions that focus on their family life. For example, a story might explore how Vegeta adjusts to being a father while still maintaining his Saiyan warrior pride. He might struggle with balancing training and spending time with his family, but Bulma is always there to keep him in check.
For the wedding of Vegeta and Bulma in my fanfiction, it was a secretive yet spectacular event. Only the closest friends and family were invited. Vegeta was hesitant at first about the whole Earthling wedding tradition, but Bulma convinced him. The wedding was held in a beautiful garden on an island. Saiyan battle music played in the background, giving it a unique touch. Vegeta was stunned when he saw Bulma in her wedding dress. Their vows were simple yet powerful, promising to be there for each other through all the battles and challenges that lay ahead, be it against powerful foes or just the daily struggles of life.