One idea could be a mercenary who is hired by a mysterious client to steal an ancient relic from Beacon Academy. He has to navigate through the various defenses and teams of Huntsmen and Huntresses.
Maybe a mercenary who was once a failed Huntsman turns to mercenary work. He then gets caught in the middle of a conflict between two powerful crime syndicates in Vale and has to choose a side while also dealing with his own moral struggles.
One idea could be a new student arriving at the school with a mysterious power that no one has seen before. This could cause both excitement and suspicion among the other students.
A plot could involve an esports competition where teams from different kingdoms in the RWBY universe compete. The story could explore how the RWBY team overcomes rivalries and strategic differences. They might also have to deal with a mysterious hacker trying to disrupt the tournament.
Well, you could have a story where all the RWBY characters swap their semblances for a day in chibi form. Ruby with Weiss's glyphs, Weiss with Blake's shadow clones, Blake with Yang's strength, and Yang with Ruby's speed. It would lead to some really funny and unexpected situations as they try to go about their normal activities at school. Or perhaps a fanfiction where the chibi RWBY teams are transported to a world made entirely of sweets. They have to resist the temptation to eat everything while also finding a way back home. A third option might be a mystery plot. A valuable item has gone missing in Beacon's chibi - version campus, and the teams have to solve the mystery of who took it and why.
One idea could be a new character arriving at the battlefield with a unique semblance that changes the tide of battle. For example, a character with the ability to manipulate time in a small area, allowing allies to get in extra attacks while enemies are frozen for a moment.
One idea could be Noctis arriving in the RWBY world and having to learn about Dust and how to use it in combat. Maybe he teams up with Team RWBY to fight against a new type of Grimm that his unique skills are well - suited to defeat.
A possible plot for 'rwby the incredibles fanfiction' is that Syndrome from The Incredibles teams up with Salem from RWBY. Syndrome offers his advanced technology to Salem in exchange for her help in getting revenge on the superhero community. The RWBY characters and the remaining Incredibles then have to find a way to stop this unholy alliance. They might start by training together to combine their different skills. Ruby could teach Dash some new acrobatic moves, and Elastigirl could show Blake how to use her flexibility in combat more effectively.
Another plot could involve a race between different teams in RWBY to claim a powerful battleship. This battleship could hold the key to some great power or knowledge. Along the way, they face various challenges and obstacles, both from each other and from external forces.
One idea could be Grimlock arriving in the RWBY world during a major Grimm invasion. His brute strength and unique abilities could turn the tide of the battle, creating an alliance between him and the RWBY team. Another plot could involve Grimlock being mistaken for a new type of Grimm at first, leading to some initial conflicts before they realize he's an ally.
One idea could be that the ring has some sort of magical power that disrupts the balance of Remnant in RWBY. Maybe it gives the wearer the ability to control Grimm in a different way. For example, instead of just attracting them, it can make them do specific tasks.
A possible plot for 'rwby for honor fanfiction' could be centered around a tournament. Characters from both RWBY and For Honor participate in a grand tournament. The tournament has unique rules that combine elements of both worlds. The RWBY characters would have to face opponents with different fighting styles from For Honor. This could lead to some interesting character development as they learn from each other and form new alliances.