One idea could be a story where Neo and Ruby are forced to team up during a special mission in a mysterious new area. They start off distrusting each other but gradually learn to work together as they face various challenges.
Perhaps there could be a story where an ancient evil threatens both universes. Naruto and Neo RWBY characters have to work together to find a way to stop it. The Akatsuki from Naruto could be involved, and some of their goals could be related to the chaos in the RWBY universe. Ruby and Naruto could form a special bond as leaders of their respective groups, leading the charge against this great threat.
One idea could be Neo using her semblance in a swimsuit-themed beach battle. Maybe she disguises as an enemy's ally and then surprises them during the fight.
One idea could be a story where Ruby and Scarlet team up to face a new, powerful Grimm that has unique abilities. Maybe it can manipulate time, adding an interesting twist to their battles.
In some 'rwby dark ruby fanfiction', there might be the idea of Ruby being corrupted by an ancient evil force. This could lead to her having to fight against her own nature as she is slowly turned into something she hates. It can also show how her friends try to save her from this dark path, which makes for a really engaging story.
One idea could be a fanfiction where Ruby discovers a new type of Dust with unique powers. This could lead her on an adventure to find out more about its origin and how it can be used to protect Remnant. Another idea is a story that focuses on Ruby's training with a mysterious mentor who teaches her new combat techniques.
One idea could be Ruby discovering she has some cheetah - like abilities. Maybe she's faster than ever and has to learn how to control this new power. It could add an interesting dynamic to her combat style and how she interacts with her team.
A third plot idea could be Ruby having to face an ancient vampire threat that is related to her new condition. Maybe she discovers that she was turned into a vampire as part of a bigger plan by an evil vampire lord, and she has to stop this villain while also coming to terms with her own vampirism. This could involve her learning about vampire lore and using it to her advantage.
One interesting idea could be Ruby taking on a more protective and mentoring role as a big sister. She might teach her younger siblings or friends combat techniques she's learned at Beacon. For example, she could show them how to better use their weapons in different combat situations.
Well, one idea could be that Ruby's dragon faunus side is awakened by a powerful relic. And then she has to quickly learn to control her new powers. Another is that she discovers she has a special bond with a dragon - like Grimm, which is really strange as Grimm are usually just evil entities. This bond could make her question the nature of Grimm and faunus.
One plot idea could be Ruby discovers she has werewolf abilities during a mission in a forest. She has to learn to control it while still fighting the Grimm. Another could be that there's a curse in Beacon Academy that turns Ruby into a werewolf, and her friends have to find a way to break the curse without hurting her.