One way to develop Bella is to explore her new identity as Carlisle's wife. She could struggle with the expectations that come with it, both from the Cullen family and from the vampire world at large. This internal conflict would add depth to her character. For Carlisle, you could delve into his feelings of protecting Bella in a new way now that they are married. He might become overprotective or have to learn to trust her more as she grows in her new role. Additionally, their relationship could be shown to evolve as they face new challenges together, which would in turn develop both characters.
In a married fanfiction, for Misaki, you could show her becoming more confident in her role as a wife. She might start taking on more responsibilities in the household and also in Takumi's business affairs if applicable. For Takumi, he could be developed to be more expressive of his emotions towards Misaki. He may learn to communicate better and share his feelings more openly, which would deepen their relationship.
Their characters can be developed by exploring their pasts. For example, delving into Nikki's previous relationships and how they've shaped her view on love and commitment. For Artem, his journey as a dancer in different countries could be explored. This would add depth to their characters and make their relationship in the fanfiction more complex and interesting.
One way is to explore the backstory of Petrova more deeply. If Bella is a fan, then showing what makes Petrova so fascinating to her through detailed backstories would be great.
For Brie Bella, her determination in the ring could be explored more. Maybe she has a secret goal that she's been striving for all her career, and Roman Reigns helps her realize it. For Roman Reigns, his leadership qualities can be developed. He could lead Brie Bella through a difficult situation in the fanfiction, like facing a powerful and corrupt wrestling promoter. This would show his ability to take charge and make tough decisions.
For Kira, you can show his growth from a reluctant hero to a confident leader within the marriage. Maybe he becomes more assertive in his beliefs. For Lacus, her kind - hearted nature can be explored more deeply as she uses it to support Kira and their new family. She could also become more politically savvy.
Elizabeth's confidence may grow even more as she becomes the mistress of Pemberley. She could start taking on more social responsibilities and use her intelligence to make positive changes in the community. Darcy, on the other hand, might become more open and less reserved as he is influenced by Elizabeth's warm and sociable nature. He may start to show his emotions more freely and be more involved in the daily lives of those around him.
For the male character, we could show more of his insecurities. Maybe he starts to worry that he's not good enough for his wife as their bookstore business grows and she seems to be more successful. This would add depth to his personality. As for the female character, we could explore her more competitive side. She could enter a local business competition and we see how her determination and drive play out. This would also show how she balances her career ambitions with her married life.
Their relationship can be developed through shared experiences. For example, they could face a common enemy together. This would force them to rely on each other and understand each other's strengths and weaknesses.
Maybe Carlisle and Bella could bond over their shared experiences of being different from the norm. Carlisle is a 'vegetarian' vampire, and Bella is a human who is in love with a vampire. They could have deep conversations about how they both struggle to fit in with their respective worlds and find solace in each other's understanding. This would add a new layer to their relationship and make it more unique.
Joey could be developed by showing his more responsible side as a husband. He was always a bit of a free spirit, but now he has to think about Melissa and their shared life. Maybe he starts taking on more household chores or financial planning, which is new for him.