One idea could be Finral getting a special power upgrade. Maybe he discovers a new spell that allows him to teleport not just himself but also others over long distances without any limitations. This would change his role in the Black Bulls significantly.
Finral's backstory about his love for women could be delved into. Maybe he had a past heartbreak that made him so eager to please women. By facing this past trauma in fanfiction, he can grow as a character and become more self - assured.
Since lemon fanfics are inappropriate, we should focus on their general characteristics from the official story. Asta is highly determined and energetic, always striving hard despite his lack of magic initially. Yuno, on the other hand, is more calm and has a natural talent for magic. They both have a strong bond as rivals and friends.
Noelle could be a great addition. Her water magic is quite powerful and she has a complex relationship with both Asta and Yuno. She could be a source of both support and conflict in the fanfic. Another good character is Luck. His lightning magic and his rather unpredictable nature can add a lot of action and excitement to the story.
Asta would likely bring a new level of determination to the Crimson Lions. His never - give - up attitude could inspire the team members during tough battles.
Asta is still alive in the manga. The story keeps evolving with him at the center of the action. There have been many difficult situations, but he manages to overcome them without dying.