One possible motivation could be his love for Bella. In the Twilight series, Edward is deeply in love with Bella. Maybe in this fanfiction, he kidnaps her out of an extreme form of protecting her. He might see some impending danger that Bella is unaware of, and he believes that by taking her away, he can keep her safe from harm.
Bella might initially be terrified. She is a human being kidnapped by a vampire, after all. She could struggle and try to escape, using her wits and any available resources. However, since she has feelings for Edward in the original story, part of her might also be conflicted, wondering if there is a good reason behind his actions.
One possible motivation could be the allure of the 'forbidden'. Edward might represent something different and exciting to Alice compared to Jasper. It's like in real life, sometimes people are attracted to the new and unknown.
Well, for one, the whole concept of their courtship would be different. Since Bella is now the vampire, she would be the one with the enhanced senses and abilities. She might be more forward in the relationship as she doesn't have the same insecurities as she did as a human. Edward, on the other hand, might be more hesitant and in awe of Bella's newfound power.
One common theme is the exploration of their love in different situations. For example, in some fanfictions, they face new threats to their relationship, like a new vampire clan that doesn't approve of their union. Another theme is the power dynamics between them. Since Edward is a vampire with special abilities and Bella is a human (at least initially), how they navigate that power difference is often explored.
Love is a very common theme. Their intense, often obsessive love for each other is a central part of most fanfictions. Another theme is the struggle between Bella's humanity and the vampire world she's drawn into. Also, the idea of family, like Edward's vampire family and how Bella fits into it.
A lot could happen. Edward could have some clashes with the vampires in the Forbidden Forest, if there are any. Bella might make friends with some of the more curious students at Hogwarts, like Hermione. And perhaps there would be a situation where Edward's mind - reading ability is either an advantage or a hindrance in the magical world. For example, he could read the minds of those planning to expose him, or it could be blocked by some powerful magic spells.
One interesting aspect could be how their relationship dynamics change. In the original, Edward was the vampire and Bella was the human, so reversing their roles might lead to a different power dynamic. For example, Bella as a vampire would have more physical strength and speed, which could make her more protective of Edward. Also, Edward as a human might struggle with his mortality compared to Bella's immortality, creating new tensions and storylines in the fanfiction.
One great fanfiction could be where Edward and Bella's relationship is explored more deeply in a different vampire society setting. For example, they might be in a vampire clan that has unique rules about human - vampire relationships.
Maybe the writer wants to explore gender - bending themes. It could be a way to break the traditional gender norms associated with the character. By giving Damon this unexpected physical trait, they might be aiming to see how the character and the story would develop in a completely different context.
One interesting story could be where Bella discovers a new power that is unique even among vampires. It adds a new twist to their relationship as Edward tries to understand this new aspect of her.