One idea could be exploring the backstory of the character in the Silver Trailer. Maybe show how they got their unique weapon and the training they went through. Another could be creating a prequel that leads up to the events in the trailer, like their first encounter with the Grimm.
Another plot idea could be a character who is mysteriously connected to the Silver Flame. They could have powers that are enhanced by it and have to hide this fact from others for some reason, like fear of being experimented on. For example, a new student at Beacon Academy discovers this connection and has to navigate through the challenges while keeping it a secret.
One idea could be exploring the backstories of the characters shown in the trailers in more depth. For example, for Ruby, you could write about her early days of training and how she discovered her scythe. Another plot could be a prequel to the events in the trailers, showing how the teams were formed. Maybe there was some sort of competition or trial that brought them together.
It could be a powerful Grimm that has a special connection to the character in the trailer. Maybe this Grimm has been hunting them for a long time and is finally about to catch up.
One idea could be a choice where the characters have to decide whether to ally with a mysterious new group in Vale. This new group seems to have some unique powers and resources, but their motives are unclear. It could lead to different story arcs depending on the choice made.
One idea could be a character getting a tattoo that has a hidden power. For example, a RWBY character might get a tattoo that glows when danger is near, like a warning sign. Another plot idea could be a story centered around a tattoo artist in the RWBY universe who creates unique tattoos for the Huntsmen and Huntresses, and each tattoo gives them a special ability or connection to the Dust energy. Maybe a tattoo that allows a character to communicate with Grimm in a strange way, adding an interesting twist to the story.
One idea could be a story where the characters from RWBY have to face a new, extremely powerful Grimm that has unique abilities. This Grimm could be immune to certain types of Dust, forcing the team to come up with creative combat strategies. Another plot could involve a tournament within the RWBY battlefield, where different teams compete not just for victory, but also for a rare and powerful relic. This would add an element of competition and strategy among the characters.
Perhaps Sasuke is mistaken for an enemy at first. His strange powers and appearance raise suspicion. But as the story progresses, it's discovered that he has knowledge of a greater threat that is coming to the RWBY world, something that might be related to his own past experiences. So he teams up with the RWBY characters to prepare for this threat.
One idea could be the RWBY characters teaming up with the Payday gang to steal some valuable Dust from a powerful and corrupt company. They'd have to use their unique skills, like Ruby's speed and Crescent Rose, combined with the Payday crew's heist expertise.
One idea could be the young RWBY characters having a mini adventure in the woods near their homes. They might discover a strange creature and try to befriend it. Another could be them having a pretend battle tournament in their backyard, with each using their unique abilities in a more innocent and unrefined way.
One idea could be exploring new Grimm species in the RWBY GP fanfic world. Maybe there are Grimm that can blend into the environment in a more advanced way, like turning into man - made structures to ambush Huntsmen and Huntresses. Another plot could revolve around a new character who has a unique weapon design that combines different Dust types in an unorthodox way, and they have to prove themselves in the academy.