A plot could revolve around a new, powerful enemy that specifically targets Team JNPR. This enemy has studied their weaknesses and uses that knowledge to try and take them down one by one. The team then has to overcome their individual insecurities and grow stronger as a unit to defeat this foe. For example, Nora might have to face her fear of being alone, while Ren has to deal with his struggle to open up more emotionally.
One idea could be that Ruby discovers she has the power of a Maiden in a moment of great danger. She then has to learn to control it quickly while still leading her team. Another could be that Weiss, as a Maiden, uses her ice powers in new and unexpected ways, like creating entire ice fortresses to protect her team from a powerful enemy. Maybe Blake, as a Maiden, is able to use her powers to communicate with the Grimm in some strange way, leading to a new understanding of them.
One interesting RWBY JNPR fanfiction could be about the team's adventures outside of Beacon. For example, a story where they explore an ancient, forgotten part of Remnant filled with new Grimm and undiscovered relics. They might face challenges that test their teamwork and individual skills in ways not seen in the main series.
One interesting plotline could be a friendly sparring match that turns into a real test of skills and teamwork for both RWBY and JNPR. Maybe there are unexpected alliances formed during the fight.
Nora Valkyrie is also quite popular. Her energetic and sometimes wild personality provides a lot of comedic and action - filled moments. Writers can play with her backstory, like her relationship with Ren and her origin as a warrior. Ren is popular too. His calm and collected nature is a great contrast to Nora's exuberance, and his own hidden depths, such as his family history, can be delved into in fanfiction.
One idea could be that the OC team is on a mission to retrieve a powerful relic lost in a dangerous, abandoned Grimm-infested city. Each member of the team has a unique skill that they have to use to overcome different obstacles, like one being able to manipulate ice to freeze the Grimm, another with super speed to outrun them, etc.
One interesting RWBY and JNPR fanfiction could be 'Teamwork and Trust'. It focuses on how the two teams work together in a mission that wasn't shown in the original series. Another is 'New Beginnings for RWBY and JNPR' which explores what would happen if the characters had to start over in a different world. And 'JNPR's Support for RWBY' shows the great support JNPR gives to RWBY during a difficult time in Vale.
Another reason is the potential for unique storylines. The main RWBY plot gives a foundation, but fanfic writers can take JNPR on all kinds of adventures. They can be in different worlds, face new enemies, or even just have a day - to - day story that shows their lives at Beacon Academy more in - depth. It allows for a lot of creativity.
I also like 'JNPR: Unity in Diversity'. This one focuses on how the different personalities in the team, like Jaune's determination, Pyrrha's grace, Ren's calmness, and Nora's exuberance, all come together to form a strong and cohesive unit. It's really interesting to see how they overcome their differences and work towards a common goal.
Romance is also a common theme. There could be stories about the relationships between members of JNPR and Rose. Maybe a love story between a character from JNPR and one from Team RWBY.
One idea could be Kirby arriving in Remnant and being mistaken for a new type of Grimm at first. Then, as the characters get to know Kirby, they realize his unique abilities can be a great asset in battles against Salem's forces.