One interesting plot could be Jasper struggling to control his past instincts while being around Bella as his mate. Maybe he has flashbacks to his more violent vampire days and has to work hard not to let that side of him show. Another could be Bella having to deal with the reactions of the Cullen family to their unexpected mating. Some fanfictions might also explore how their relationship develops in the face of other threats in the Twilight universe.
One interesting plot could be Jasper helping Bella to control her new vampire abilities in a unique way. Maybe he uses his military experience to train her. Another plot could be them exploring the world together as mates, facing different vampire clans and their unique cultures.
The two main characters are Jasper and Bella. Jasper is a vampire who has seen a lot in his long undead life. His past experiences shape his character and how he approaches his relationship with Bella. Bella is the human who becomes his mate. She has her own insecurities and strengths. In the fanfiction, their relationship is explored through their different personalities, with Jasper's vampire nature and Bella's human nature often creating interesting situations and storylines.
In some 'bella is jasper's mate fanfiction', a great plot is their journey to understand each other's pasts. Since Jasper has his own complex history with his vampire life and Bella has her experiences in the Twilight world. They might share stories that make their bond even stronger. Also, there could be a plot where they have to work together to protect their loved ones from a common enemy, which tests and deepens their relationship.
A plotline could involve Jasper and Bella forming a closer bond as friends first. They might start sharing their deepest fears and secrets, which in turn leads to a different kind of relationship. For example, they could confide in each other about their struggles with being a vampire (Jasper) and being in a world full of the supernatural (Bella). This could gradually develop into a romantic relationship that is based on a strong foundation of friendship and mutual understanding.
One common theme is the idea of redemption. Often, Jasper might be dealing with his past as a vampire, and the OC helps him find a new path. For example, in some stories, the OC's love makes him see that he can be more than his past actions.
One idea could be that Jasper and Bella discover a unique bond that helps them face the challenges in the vampire - human world together. For example, Bella's unique ability to resist vampire powers in the original story could be enhanced when combined with Jasper's gift of manipulating emotions.
One interesting plot could be that they explore a mysterious island during their honeymoon. They might discover ancient ruins and have to face some unexpected challenges together, which deepens their bond.
One common theme is the exploration of an alternative relationship. Since in the original Twilight story, Bella is mainly with Edward, fanfictions often explore what could be between her and Jasper. Another theme is Jasper's past and how it affects his relationship with Bella. His experiences as a vampire in different eras are often delved into.
One common theme is the exploration of their unique connection. Since Jasper has the ability to sense and manipulate emotions, and Bella is often a bit of an enigma in the vampire world, their connection can be really interesting to explore. For example, in many fanfictions, Jasper helps Bella control her own emotions better.
Overcoming differences is another theme. Since the OC is a created character, there are usually differences between them and Jasper, whether it's in their backgrounds, abilities, or personalities. The fanfictions often show how they bridge these gaps. For example, in some stories, the OC might be from a different supernatural group, and they have to learn to coexist and love each other. Another aspect is the theme of loyalty. Once they become mates, they show loyalty to each other, which is often tested in the face of various threats and challenges in the fictional world.