One idea could be Ruby trying to infiltrate the White Fang to understand their motives better. Maybe she disguises herself as a new recruit and has to navigate their complex hierarchy and various factions within the group.
Another plot could involve Ruby befriending a reformed member of the White Fang. This friendship could then be a catalyst for change within the organization as Ruby's positive influence spreads. For example, she could introduce the idea of non - violent protest to the more radical members through her new friend.
A more action - packed plot could be Ruby getting caught in the middle of a power struggle within the White Fang. There could be different groups vying for control, and Ruby has to use her skills to not only survive but also try to broker peace between the warring factions. She might have to team up with some of the more reasonable White Fang members to fend off the more extreme ones.
An OC that is a spy within the White Fang for a different organization. They are trying to figure out the White Fang's true intentions and stop any potential terrorist activities. This would involve a lot of secrecy, betrayal, and moral dilemmas as the OC gets closer to the truth.
One idea could be that Ruby and Coco team up for a special mission in a dangerous, uncharted part of Remnant. They face new Grimm and have to rely on each other's unique skills to survive. Coco's fashion - sense - related weaponry could combine with Ruby's speed and scythe skills in interesting combat sequences.
A really interesting plot would be if Ruby's Reaper form was somehow connected to an ancient prophecy in the RWBY world. Maybe it was foretold that a Reaper - like figure would either save or doom Remnant. This would put Ruby in a very difficult position, with different factions having different views on her and her new form. Also, a plot where Ruby has to team up with some unlikely allies while in her Reaper form to take on a common threat could be cool. These allies could be former villains who see the greater danger that requires Ruby's power.
One idea could be Ruby having to relearn her combat skills while being deaged. It would add an element of struggle and growth as she tries to regain her former abilities. Maybe she forms new friendships with characters she already knew in a different way because of her new, younger perspective.
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.
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.
Well, in some fanfictions, a male Ruby might be from a different background than the original Ruby. This could lead to an interesting dynamic with Weiss. For example, he could be from a more noble family, which causes some initial friction with Weiss, who is also from a noble background. As they work through their differences, a White Rose relationship begins to develop. It could involve them facing off against a new type of Grimm that only male Ruby's special skills can help defeat, bringing them closer together.
One plot idea could be Ruby and Winter teaming up for a special mission. Maybe they have to infiltrate an enemy stronghold. Ruby's speed and Crescent Rose could be combined with Winter's ice powers and combat skills for some epic fight scenes.
One idea could be Ruby and Blake getting lost in a mysterious forest during a mission in Volume 5. They have to rely on each other's skills, Ruby's speed and Blake's stealth, to find their way out. Another could be that they discover a long - lost relic together and have to protect it from a group of Grimm.
One plot idea could be Qrow training Ruby in some special combat techniques that are unique to his own fighting style. This would allow Ruby to gain new skills and also strengthen their bond as family members.