Maybe in the fanfic, a villain has the stop - time ability. This causes chaos as they start stealing important artifacts while everyone else is frozen. The RWBY team has to find a way to counter this power, perhaps by teaming up with a time - wizard who teaches them how to move in stopped time.
One idea could be a character using the time - stop ability to save a teammate from a deadly attack. For example, Ruby could stop time to move Weiss out of the way of a Grimm's strike. Another could be a villain using it to set up a complex trap that the heroes have to figure out how to escape from once time starts again. Maybe they freeze time to manipulate the environment and make it more dangerous for the RWBY team.
Maybe a character from the future RWBY world travels back to the time when the Huntsman academies were first founded. They could introduce new fighting techniques or ideas that were developed in their time, which would have a huge impact on how the early Hunters and Huntresses are trained.
One interesting concept could be the exploration of character relationships during the time stop. For example, how characters might interact or reveal hidden feelings when time is frozen. Another could be the strategic use of the time stop ability in battles. Characters might use this time to plan their next moves, analyze their opponents' weaknesses, or set up elaborate traps.
Well, perhaps the OC's time loop semblance only activates when they are in great danger. So, in a battle against a powerful Grimm, they start looping. In each loop, they try different strategies to defeat the Grimm, and along the way, they discover new abilities of their teammates. They could also use the time loop to prevent a major disaster from happening in Vale, like a terrorist attack planned by Roman Torchwick.
Another interesting concept is if an enemy from the past is brought to the present in a time travel accident. Maybe Salem is accidentally brought forward in time. This would force the RWBY characters to face her with their current skills and knowledge, leading to intense battles and strategic planning as they figure out how to send her back or defeat her in this new time.
One plot idea could be that a character from RWBY gets transported to the world of Overlord. They might have to navigate the power - hungry and often dangerous world, trying to find a way back home while also dealing with the various powerful beings in Overlord. For example, Ruby could end up in the Tomb of Nazarick and have to figure out how to interact with the Floor Guardians without getting killed.
One idea could be exploring a different backstory for one of the main characters. For example, Ruby could have grown up in a more isolated part of Remnant and had to learn combat skills in a very different way. Another could be a time - travel plot where a character goes back in time to change a major event in the RWBY universe. Maybe they try to prevent the fall of Beacon earlier in the story, which would have a huge impact on all the characters and their relationships.
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 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.
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.