One way the fanfiction expands on the characters is through their interaction with new elements. Shirou, who was mainly dealing with his own world's magic system, now has to deal with Saber's different magical heritage. This forces him to adapt and learn, showing his intellectual side more. Saber, being from a different time and place, in a crossover might have to face modern - day ethics and values. This challenges her traditional beliefs and shows how she can either hold on to them or evolve. Their relationship in the crossover also allows for exploring their mutual respect and how they can support each other in ways that were not as evident in the original story.
Well, a fanfiction like this could be really interesting. Maybe it could start with Rin and Shirou being somehow transported to the DxD universe. Saber could end up being a powerful ally or a mysterious figure that both the devils and the heroes in the DxD world are curious about. And Astaroth, being a powerful demon in the DxD lore, would surely have an interesting dynamic with the Fate characters. It could be a story full of magic battles, political intrigue within the devil society, and the clash of different ideologies from Fate and DxD.
In the canon, their relationship is more restrained. But in lemon fanfiction, it often explores a more passionate and romantic side of their relationship. Canon focuses on the overall story and battles, while the fanfiction delves deeper into their personal feelings for each other.
In this crossover, Shirou's projection magic could be incorporated by having him project not only weapons but also magical items from the DxD universe. This would show his adaptability. Rin could combine her magic with the devil - related magics in DxD, creating new spells. Saber's noble phantasm could be the key to solving certain major problems in the DxD world, like a powerful threat that even the devils can't handle. Astaroth's powers could be used to test the limits of the Fate characters' abilities, forcing them to grow and develop new strategies to deal with him.
It could start with distrust. Saber Alter is different from the original Saber, and Shirou might be cautious. But as they face challenges together in Camelot, like battles against dark creatures, they start to rely on each other. This gradually builds respect and then a deeper connection.
In fanfiction, Shirou and Saber's love is often depicted as a complex and beautiful relationship. It's a love that transcends their different natures. Shirou, with his strong sense of justice, is drawn to Saber's noble and powerful presence. Their love story can be full of moments of understanding and mutual growth.
For Shirou, his character can be developed by showing his growth in combat skills specific to the Camelot era. He could learn new sword - fighting techniques from Saber Lily. His ideals can also evolve as he experiences the different values in Camelot, becoming more confident in his own beliefs.
Fanfiction often delves deeper into the characters' backstories. For example, we might learn more about Summer's family life and how it influenced her views on relationships.
Well, a great storyline might involve Shirou and Saber swapping roles in some way. For example, Saber having to take on Shirou's daily life tasks, like going to school or doing mundane jobs, while Shirou has to lead in battles like Saber usually does. This role - reversal can bring out a lot of comical and also deep character - development moments. Also, a plot where they are in a parallel universe where their fates were different from the original story and they have to come to terms with these new versions of themselves.
In fanfiction, Okabe's mad scientist persona can be further developed. Maybe he's even more eccentric or has some new quirks that are specific to the fan - created story. It could show his thought process in more detail when it comes to his feelings for Makise.
It can expand on the theme of surveillance. In the original '1984', we see the omnipresent Big Brother watching. But in fanfic, it might show how the people start to fight back against this surveillance. They could use hidden methods to communicate without being detected, which is an expansion of the idea of resistance against the all - seeing state.