Well, perhaps they first time could be a part of a healing process for both of them. Jacob has his own traumas related to his shape - shifting and Bella has been through a lot in her relationship with Edward. They could find solace and a new beginning in each other, and this first time could symbolize that fresh start in their relationship.
One possible plot could be about the challenges of raising a baby in the world of Jacob and Bella. Maybe the baby has some special powers that they have to protect it from the wrong people.
One idea could be the new pack facing a mysterious and powerful threat that they have to overcome together. Maybe a new type of supernatural being that they've never encountered before.
A really cool plot for this fanfiction could be that Jacob and Bella accidentally swap bodies due to a strange spell. This leads to a series of comical and also deep - thinking moments as they try to understand each other's lives better. They also have to figure out how to reverse the spell before it's too late. Meanwhile, they learn more about their feelings for each other in this unique situation.
One idea could be exploring the unique powers the child might inherit. Since Jacob is a werewolf and Bella has her own vampire - related traits, the child could have a blend of superhuman abilities like enhanced strength, speed, and perhaps even some form of mind - reading or connection to nature. Another idea is to focus on the child's upbringing in a world where vampires and werewolves co - exist. How would they navigate the complex politics and relationships between the two groups? Also, the child's love life could be an interesting aspect to write about. Would they fall in love with a human, a werewolf, or a vampire?
One possible plot twist could be that an old enemy shows up at the wedding. For example, a vampire from a different coven who has a vendetta against either the Cullens or the werewolves. Another could be that Jacob has a premonition right before the wedding that something bad will happen to Bella in the future, which makes him hesitant to go through with it. Or perhaps a long - lost relative of Bella's arrives and reveals a big family secret that shakes things up.
Some fanfictions in this theme might focus on the reactions of the Cullen family. They could be either accepting or having some sort of conflict due to Bella's situation with Jacob. Also, the story could explore how Bella herself copes with the physical and emotional changes of being pregnant, especially in a world filled with vampires and werewolves.
One plot idea could be Bella struggling to choose between her vampire life with Edward and her deep friendship with Jacob that has the potential to turn into more. Another could be Jacob trying to protect Bella from a new vampire threat while also dealing with his feelings for her. Maybe a plot where Bella discovers a new power as a vampire that Jacob has to come to terms with.
One idea could be that they finally have a moment of pure peace and just talk about their future. They might share their dreams and fears under the moonlight. Another could be a traditional Native American ceremony element incorporated into their wedding night, like Jacob sharing a special tribal story with Bella.
One idea could be that Bella travels back to a time when vampires first emerged. She could try to change the history of vampire - human relations, maybe prevent some of the early vampire - made disasters. Another idea is she goes back to a time in her own family's history and discovers secrets that shape her present. For example, she might find out that her family has some hidden connection to the supernatural world long before she became involved with Edward.
Including the influence of their families and friends. Jacob's pack might have an opinion, and Bella's friends in Forks could also play a role. Their reactions and how Jacob and Bella deal with them can make the relationship more believable. Also, showing how they handle their differences. Jacob is a werewolf and Bella is human, so things like their different life expectancies and values need to be addressed in a way that makes their relationship seem real.