Perhaps there's a plotline where Summer's resurrection is part of a larger mystery. It could be related to an ancient evil that she was somehow involved with before her death, and now she's back to stop it. She might have to convince the other characters that she's really on their side and not some sort of imposter. The fanfiction could explore how the other members of Team RWBY react to her return, especially if they have mixed feelings about her being back.
A plotline could be that there is a prophecy involving Summer and Ruby. As Ruby grows stronger, she starts to notice strange things happening around her that seem to be related to this prophecy. She then starts to search for more information about it and discovers that it has something to do with Summer's final mission. Ruby decides to follow in her mother's footsteps to fulfill the prophecy. In the process, she uncovers secrets about her family and the world of RWBY that were long hidden. This could lead to her developing new relationships and facing moral dilemmas as she tries to stay true to her mother's legacy.
Another could be a story where Lemon discovers an old diary or artifact that belonged to Summer Rose, and through it, she uncovers some long - forgotten secrets about Summer's past adventures and relationships. This could lead to Lemon getting involved in something much bigger than herself.
In addition, villains from the RWBY universe could also be main characters in this fanfiction. If Summer's resurrection is part of some grand plan by Salem, for example, Salem herself or her minions could play important roles. They might try to manipulate Summer or use her for their own evil purposes. And this would lead to many conflicts and battles in the fanfiction as Team RWBY and their allies try to protect Summer and stop the villains.
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.
One possible plotline could be a character sacrificing their own powers to save their friends from a powerful enemy. For example, Ruby might give up her Silver - eyed Warrior abilities to stop Salem's latest scheme and protect her team.
Well, in some rwby mugetsu fanfiction, there might be a plotline where the characters have to adapt to a new world that combines the two settings. They could struggle with understanding different cultures and magic systems. Maybe Weiss has to learn how to use her Glyphs in a world where the rules of magic are more like those in Mugetsu. This would lead to her character growth as she overcomes these challenges.
One possible plotline could be a character facing public shaming in the RWBY universe, perhaps due to a failed mission or a misjudgment. Another could involve a character being humiliated in a social setting within the school or among their team.
Another plotline could involve the reincarnated character trying to change the fates of the main RWBY characters. They might know about certain events that are going to happen in the future of the RWBY story and work towards preventing tragedies or enhancing the characters' growth in different ways. Maybe they try to save Pyrrha from her doomed fate at the hands of Cinder.
One interesting RWBY Summer Rose fanfiction could be about her untold adventures. For example, a story where she embarks on a solo mission to uncover a hidden Grimm lair. It could explore her combat skills and strategic thinking in more detail.
In RWBY Summer Lives fanfiction, often there are stories that focus on Summer's relationships. It could be her relationship with her team members. How she trained Ruby, or the bond she had with Yang's mother. These relationship - centered stories can add a lot of depth to the character of Summer.