Well, while Lucy and Lula are the main characters, there could also be other supporting characters. For example, there might be Lula's family members or friends in the time period that Lucy travels to. These characters could add more depth to the story, like Lula's parents who might be initially suspicious of Lucy but then come to accept her as she helps Lula in various ways.
Well, it could be that Lucy goes back to a time when Lula was in a difficult situation and she uses her modern knowledge to help Lula out. Maybe she helps Lula with some sort of social issue or a personal problem that was prevalent in that time.
Lucy may also come across ancient warriors. For example, she could meet a Spartan soldier and be amazed by his combat skills and strict discipline. They could have a brief encounter where the Spartan is curious about this strange girl from another time.
Well, she might meet historical figures. For example, she could encounter Cleopatra and have an interesting conversation about ancient Egyptian politics and culture.
Well, obviously she'll interact with her past self. It would be really interesting to see how she reacts to seeing a younger and more naive version of herself. She could also meet characters who are no longer alive in the present. For example, if there were any great wizards from the past who played important roles in the history of magic. Additionally, she might cross paths with some of the villains from the past who were causing trouble long before the current villains in the story. This could change her perspective on the whole conflict in the present.
One interesting plot twist could be that when Lucy goes back in time, she discovers that her family has a much darker secret than she ever knew. Maybe they were involved in some sort of magic that was considered forbidden in the past. Another could be that she accidentally changes the future in a way she didn't expect, like making her friends not become the people she knew them as. And perhaps she finds out that an enemy in the present was actually once an ally in the past, and she has to figure out what went wrong to turn them into an enemy.
She could meet her younger self. This would be an interesting encounter as she could offer advice and guidance to her younger version. Maybe she could help her younger self to be less afraid of her powers.
He could change the course of major events. For example, he might prevent the rise of a powerful villain. This would have a huge impact on the entire galaxy. Maybe he could save some characters who died in the original timeline.
One interesting aspect could be that Luke goes back to a time when the Sith were just emerging. He could try to root out the Sith threat before it became as powerful as it did. He might have to be very careful not to disrupt the timeline too much, but his Jedi wisdom could be a great asset in this time - traveling adventure.
In this fanfiction, Sora might change key events. Maybe he could prevent some of the tragedies that occurred in the original story. For example, he could save a character who was lost before.