One possible plotline could be Anakin having to re - learn the ways of the Force as a child while also dealing with his past memories. Another might be how the other Jedi react to this de - aged Anakin, whether with suspicion or a sense of protectiveness.
Some fanfictions might explore how Anakin's de - aging affects the overall timeline of the Star Wars universe. For example, his actions as a de - aged version could potentially prevent certain events from happening or set off a whole new chain of events. Maybe he could change his relationship with Palpatine. Since he has the wisdom of his older self, he might be more aware of Palpatine's true nature earlier and avoid falling into the dark side this time. This would then have a huge impact on the fate of the galaxy, and the story could focus on how the other characters adapt to this new situation.
A great plotline might involve the deaged characters interacting with their younger selves' memories. Weiss could be haunted by her family's expectations in a new light, as if seeing them for the first time all over again. This could lead to her making different choices and growing in a whole new direction.
Yoda would be another character. As one of the wisest Jedi, he could sense the strange situation with Anakin and offer his unique perspective. He might be more patient with a child - like Anakin, teaching him important Jedi lessons and trying to ensure that Anakin doesn't go down the same dark path as he did in the original timeline.
One interesting plotline could be Severus having to take care of a deaged Harry. He might struggle with his initial dislike for Harry but gradually grow to understand him better in this new situation. For example, he could teach the young Harry some basic potions skills, which would be a unique bonding experience.
One interesting plotline could be Harry and Draco being deaged and having to rely on each other in a world that seems new to them again. They might form an unexpected friendship as they don't have the pre - conceived notions from their older selves. For example, they could team up to solve a mystery in Hogwarts that only they, with their combined knowledge from before, can figure out.
One possible plotline could be Anakin, in a redeemed state, secretly protecting baby Luke from the remaining threats in the galaxy. He uses his remaining Force abilities to shield Luke from danger without revealing his identity.
One possible plotline could be Anakin's redemption taking a different turn. Instead of dying, he lives and uses his newfound Light Side strength to help Luke rebuild the Jedi Order. He could become a mentor to the new generation of Jedi, sharing his experiences and knowledge, which is a far cry from his previous role as Darth Vader.
A typical plotline in Loki deaged fanfiction is Loki being deaged due to some magical mishap. This then leads to him being in a situation where he has to rely on others, which is a big change for him. For instance, he might have to rely on the Avengers (if it's set in that universe) for help. Another aspect could be that deaged Loki has to face his insecurities from his childhood all over again. This can be really interesting as it shows a different side of Loki, a more vulnerable side that we don't often see in the original stories. There are also fanfictions where deaged Loki tries to regain his old age as quickly as possible while still causing some trouble along the way.
Perhaps he goes back in time and decides to train himself better. He could focus on mastering his emotions from the start, which might change the entire course of the Star Wars saga. He might also try to save his mother in a more effective way, without succumbing to anger and hatred.
Some fanfictions explore their relationship in the context of the Jedi Council. Since Anakin was often at odds with the Council, and Aayla was more in - line with the traditional Jedi ways, it creates an interesting dynamic. Maybe Anakin has an idea for a new strategy in the war, and Aayla has to decide whether to support him or side with the Council, which can lead to a lot of character development.
A unique plotline could be Percy being deaged and having to hide his identity from the new demigods at Camp Half - Blood. He has to pretend he's a new camper while secretly trying to find a way to reverse the deaging.