One interesting plotline could be the exploration of the God of Light's past and his relationship with other deities in the RWBY universe. Maybe how he came to be and what his true intentions are for the world of Remnant.
A third plotline could be a what - if scenario where the God of Light takes a more active role in the events of RWBY. Instead of being a somewhat distant and mysterious figure, he directly intervenes in the battles between good and evil. This could change the dynamics of the story completely, as the characters have to adjust to having a powerful deity on their side or, in some cases, working against them if they misunderstand his intentions.
Well, perhaps there's a plotline where the god brothers get involved in a conflict in RWBY. They might take sides, which would completely change the dynamics of the fight. For example, if they side with the villains, the heroes would have to find a way to either convince them to change sides or develop new strategies to oppose them. It could also be that a plotline focuses on how the god brothers' existence impacts the magic and Dust in the RWBY world.
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.
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 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 RWBY God of Light and Darkness fanfiction, a cool concept could be the idea of characters being chosen or influenced by these gods. Maybe a character gains special powers from the God of Light to fight against the encroaching darkness. Also, the fanfiction might delve into the moral implications of the actions of these gods and how the characters react to them.
One interesting plotline could be the characters facing a new and powerful Grimm threat that they have to overcome together. This would test their skills and teamwork.
Perhaps there could be a plot where Ruby has to keep her status as a Maiden a secret from her friends at first. This could lead to some interesting misunderstandings and internal conflict as she tries to protect them without revealing the truth.
Perhaps a plot where a dragon rider is from a different dimension and has to adapt to the world of RWBY. They could bring unique skills and knowledge that help the RWBY gang in their battles and also learn a lot from them in return. This could involve cultural exchanges as well as combat strategies.