Fanfiction about Bella's sister and Caius in Twilight: What are some interesting plot ideas?

There could be a story where Caius has a change of heart after meeting Bella. In the Twilight world, Caius is known for his strict and often cruel ways. But when he encounters Bella, he starts to question his own beliefs. Maybe Bella gets lost in the Volturi territory and Caius finds her. Instead of punishing her, he is intrigued by her. This could lead to a story of him trying to understand her human - vampire relationship with Edward from a different perspective. He might even start to envy Edward in a way, which could create a whole new dynamic in the fanfiction.

Well, perhaps Bella's sister is a half - vampire herself. She was born from a vampire who didn't fully turn her mother. This sister could struggle with her identity, not fully fitting in with either humans or vampires. She might be drawn to the Cullens because of their 'vegetarian' lifestyle but also be scared of them. She could also be friends with Jacob before Bella even arrives in Forks, and Jacob has to keep her secret from Bella until the right time.

One plot idea could be that Bella's sister discovers she has a special power as a vampire, like being able to see the future. This could lead to her trying to prevent bad things from happening to her family and the Cullen family. Another idea is that she struggles with the morality of being a vampire while also being in love with a human. She might try to find a way to exist without harming humans, which would create a lot of internal conflict.

One idea could be that the soulmate connection defies the natural enmity between the Twilight world and the Mikaelson's world. Maybe the soulmate bond allows them to communicate telepathically across different realms. For example, Caius could be in his vampire world in the Twilight universe while his soulmate is in the Mikaelson's world of witches and vampires, and they share dreams and thoughts that gradually bring them closer.

One idea could be that Bella's sister discovers a hidden power within herself. Maybe she can communicate with animals and uses this ability to protect the town from an unknown threat.

One idea could be that Bella and Rosalie have to team up to protect the Cullen family from a new vampire threat. They start off disliking each other but as they face challenges together, they develop a mutual respect.

Maybe in a fanfiction, Demetri discovers that Bella has a hidden power that not even the Cullens are aware of. He then has to decide whether to report it to the Volturi or keep it a secret and help her develop this power. This could create a complex relationship between them, full of trust issues and moral dilemmas.

One plot idea could be that Felix, instead of being a villain, becomes Bella's secret protector in the Twilight world. He might sense some unique power within her that even the Cullens are unaware of. This could lead to a series of adventures where they have to hide their alliance from both the Volturi and the Cullens.

One idea could be that Bella is a vampire from the start but has been in hiding. She could be on a mission to uncover a secret vampire society that has been causing trouble in the Twilight world. This would change her relationship with the Cullens as she'd be more of an equal, not a fragile human.

One idea could be Carlisle having to protect Bella from a new vampire threat that is specifically targeting her for her unique connection to the Cullens. Maybe a group of nomadic vampires who are jealous of the Cullens' lifestyle.