One idea could be creating a robot OC that has the ability to transform into different forms inspired by the various Grimm in RWBY. For example, it could shift into a Beowolf - like form for combat situations. Another idea is a robot OC designed by a villainous character in the RWBY universe but ends up having a change of heart and joins the heroes. You could also have a robot OC that has a unique Dust - based power system, which is different from the normal ways Dust is used in RWBY.
Another interesting concept is a robot OC that was created by a villain but has a change of heart. This robot could struggle with its programming and new - found sense of morality. It might have to hide its true identity from both heroes and villains while trying to do good in the world of BNHA.
Perhaps the OC is a creation of a mad scientist who wants to use Ultron's technology to enhance their own creation. The OC then rebels against the scientist's control and teams up with Ultron for mutual benefit, leading to a series of adventures where they face various challenges together, such as fighting off military forces trying to destroy them.
One idea could be to cross your original character (OC) with the world of RWBY and have them be a transfer student at Beacon Academy. They could bring unique skills or powers from their own world, like a magic system that RWBY doesn't have. Another idea is to have the OC be from a different time period and get thrown into the RWBY universe, causing all sorts of chaos and new storylines. For example, an OC from a steampunk world with advanced machinery could introduce new tech to the RWBY characters.
Another interesting concept is an OC that is part of a secret society in the RWBY Cold world. This society could be dedicated to protecting ancient ice - related artifacts. The OC would have to navigate the politics of the RWBY universe while also keeping their society's secrets. They might form alliances with the main RWBY characters to fend off villains who want to use the artifacts for evil.
Well, you could have an OC who is an alien with special powers that are different from the normal Semblances in RWBY. For example, they can control gravity in a way that gives them an edge in combat. Or an OC that is a diplomat from a space - faring civilization trying to make peace between different kingdoms on Remnant. Also, an OC who was stranded on Remnant after their spaceship crashed and has to adapt to the world while also trying to find a way back home.
One idea could be an OC with a unique weapon. For example, a weapon that can transform into multiple forms like a sword that can split into two daggers. This would add an interesting dynamic to battles in the RWBY universe. Another idea is an OC with a special semblance related to time manipulation. They could slow down time to gain an advantage in combat or speed up time to heal wounds faster.
One idea could be to create a sibling who has a different combat style. For example, while Ruby uses her scythe and speed, the sibling could be more of a strategic fighter, using traps and illusions. Another idea is to explore their relationship dynamic. Maybe the sibling was always in Ruby's shadow and had to struggle to find their own identity. Or perhaps they have a special bond because of a shared trauma from their past.
Another plot could involve the OC reincarnating into an existing character's body. This would lead to a lot of internal conflict as they try to adjust to the new identity while still having memories of their past self. They could also use their new position to change the course of events in the RWBY universe.
Well, you could have an OC who is a tech - savvy dragon slayer. They create all sorts of gadgets and gizmos to help them in their dragon - slaying quests. For instance, they might have a drone that can scout out dragon lairs from a distance. Their backstory could involve a tragic event where a dragon attacked their village, and they vowed revenge. As for their appearance, they could have a cool, steampunk - like style with goggles and mechanical parts on their clothing. This would make them stand out in the RWBY universe. They could also team up with some of the main RWBY characters, teaching them about dragon - slaying techniques and learning from the Huntsmen and Huntresses about fighting Grimm.
One idea could be an OC who is a Hitman but has a change of heart after encountering the RWBY characters. Maybe they start to see the value in protecting the innocent rather than just taking contracts.