A really cool plot for this fanfiction could be that an ancient evil has awakened in the Pokemon world that is also a threat to Ben's world. Ben and his friends, along with some of the main Pokemon trainers like Misty and Brock, embark on a journey. Ben discovers that some of his alien forms have unique interactions with certain Pokemon. For instance, his water - based aliens can communicate with water - type Pokemon in a special way. They have to combine their skills, the Pokemon's powers and Ben's alien powers to defeat this ancient evil.
One idea could be that Ben uses his Omnitrix to transform into a Pokemon - like form. For example, he could turn into a fire - type alien that has the abilities of a Charizard. Another plot could involve Ben and Ash Ketchum teaming up to stop a powerful villain who is trying to capture all the Pokemon and use the Omnitrix for evil purposes. Maybe there's a device that can fuse Pokemon with Ben's aliens, creating super - powerful hybrids.
Well, a plot might involve a device in the Pokemon world that can temporarily give trainers the ability to transform like Ben. But it has a side - effect of attracting some of Ben's most dangerous foes. So, the trainers and Ben must work together to fight off these threats while also dealing with the chaos that the newfound powers are causing in the Pokemon world. They could also learn from each other's fighting styles and techniques during the battles.
One idea could be a crossover where the Miraculous heroes and Ben 10 team up to fight a common enemy. Maybe an alien villain that is immune to the powers of the Miraculous but Ben's alien forms can counter. Another could be a situation where Ladybug's Lucky Charm combines with one of Ben's alien gadgets to create a super - weapon. And a third could be a story where Ben gets akumatized and the Miraculous heroes have to figure out how to save him without using brute force as his alien forms are very powerful.
One idea could be that the characters from RWBY and Ben 10 universes team up to fight a common enemy that threatens both their worlds. For example, a powerful alien race in the Ben 10 world that has somehow found a way to access Remnant (the RWBY world) and is causing chaos.
Maybe in the fanfiction, Attea is in trouble on her home planet and Ben, being the hero he is, goes to help her. Along the way, they discover a long - lost secret about their two species that changes their relationship forever. This could involve some cool battles and new alien forms for Ben to use.
One idea could be that Summer and Ben team up to rescue a rare and endangered Pokemon. They face various obstacles like rough terrains and other Pokemon trainers who want to capture the Pokemon for themselves. Another plot could be that they discover a hidden power within a certain Pokemon they are protecting, and they must keep it safe from an evil organization. Maybe there's a mystery surrounding an old Pokemon Ranger relic, and Summer and Ben have to solve it together.
Perhaps a story where an old enemy of Ben's targets Rook to get to Ben. Ben feels guilty and protective. They go on the run, hiding in different places across the galaxy. Along the way, they meet some interesting characters who help them. In the end, they face the enemy together, with Ben using his Omnitrix and Rook using his upgraded Proto - Tool to defeat the bad guy.
One idea could be the main character being reborn as a Pikachu and having to navigate the world with its electric powers while making friends with other pokemon. Another could be being reborn as a Eevee and having the unique ability to evolve into any form at will, which causes both envy and admiration among other pokemon. Maybe the reborn pokemon has memories of being a human and uses that knowledge to outwit trainers and other threats.
One interesting plot could be that Ben, using his Omnitrix, accidentally lands in the Pokemon world. He teams up with Ash and Pikachu to stop an evil organization that is trying to use both Pokemon and alien technology. For example, they might be creating hybrid creatures using Pokemon DNA and alien powers. Ben's different alien forms could have unique interactions with the Pokemon. His Four Arms form could be really strong in Pokemon battles, while his XLR8 form could be used to quickly traverse the Pokemon world to reach different areas in time to stop the villains.
A fanfiction plot could be about a new threat that is specifically targeting the Omnitrix and the Power Rangers' power source. Ben and the Rangers have to figure out how the enemy is doing this and stop them. Along the way, they discover a hidden connection between the two power systems that was unknown before. There could be some character development for both Ben and the Rangers as they struggle to protect what they hold dear.
One idea could be that an alien vampire infiltrates Ben's team. It pretends to be a friendly alien at first but then starts to slowly drain the energy of the other aliens. Ben has to figure out a way to expose it without endangering his friends.