In a Ben 10 and Star Wars Rebels fanfiction plot, the villains could team up. The Empire could make a deal with some of Ben's most dangerous alien enemies. Ben and the Rebels would then have to put aside their differences and work together. Ben would use his alien forms' unique abilities. For instance, XLR8's speed could be used to quickly gather intelligence or escape dangerous situations. The Rebels would contribute their knowledge of the Star Wars universe and their combat skills. They would have to learn to trust each other to defeat this new combined threat.
Well, a cool plot could involve the Rebels finding the Omnitrix. Maybe Ezra discovers it and accidentally activates it, transforming into different Ben 10 aliens. This would be a huge advantage for the Rebels but also a bit of a problem as they try to figure out how to control the transformations. And Ben could show up trying to get his Omnitrix back, but then decides to stay and help the Rebels fight the Empire.
One possible plot could be that Master Chief somehow gets transported to the Star Wars Rebels universe. He teams up with the rebels to fight against the Empire. His advanced armor and combat skills would be a great asset. Maybe he has to face off against Imperial Inquisitors and uses his Spartan training to outwit them.
One interesting plot could be Naruto and his friends getting stranded in the Star Wars Rebels universe. Naruto's ninja skills would be quite a shock to the Rebels. He could use his shadow clone jutsu to create distractions during battles against the Empire. His ability to harness chakra might be seen as a new form of the Force by some characters, leading to some interesting exchanges about power and its uses.
One possible plot could be that Ben Tennyson and his Omnitrix somehow get transported to the Star Wars galaxy. Ben might team up with the Jedi to fight against the Sith. His alien forms could provide unique combat abilities in the Star Wars universe. For example, Four Arms could be a powerful physical fighter against stormtroopers, and Heatblast could deal with enemies in hot environments like Tatooine's deserts.
One idea could be a crossover with the original Star Wars trilogy characters. For example, having Luke Skywalker meet the Rebels crew and learn from their guerilla warfare tactics against the Empire. It would be exciting to see how their different fighting styles blend and how they interact with each other.
One plot idea could be that a character from Clone Wars gets accidentally sent to the time period of Rebels. For example, Ahsoka Tano could end up in the middle of a battle between the Rebels and the Empire. She might use her knowledge from the Clone Wars era to help the Rebels in unexpected ways, like teaching them some old Jedi combat techniques that were lost over time.
Perhaps there could be a lost Mandalorian artifact that the Rebels accidentally discover. This draws the attention of a group of Mandalorians who think the Rebels are trying to steal it. As a result, they have to work together to figure out the true purpose of the artifact and face off against a common enemy who also wants it for their own evil plans.
There are several great plot ideas. For instance, imagine a situation where Yoda, before his death, set in motion a series of events that are only starting to unfold during the Rebels' time. Maybe he planted the seeds for a new Jedi order in a very secretive way. A young Rebel might stumble upon these secrets. Another idea is that Yoda's teachings, which were thought to be lost, are rediscovered by the Rebels through an ancient Jedi artifact. This discovery changes the way they approach the fight against the Empire. And what about a story where Yoda's influence reaches out to a non - Force - sensitive character in Rebels, inspiring them to do great things for the Rebellion in a different way?
One idea could be that Ben uses his Omnitrix to transform into alien forms that have unique abilities to survive in the Star Wars universe. For example, a heat - resistant alien to withstand the heat of Tatooine's deserts or a species with enhanced senses to navigate the dangerous jungles of Kashyyyk. Another idea is that the Galactic Empire somehow gets hold of the Omnitrix and tries to use it for their own evil purposes, leading to Ben having to team up with the Rebel Alliance to get it back.
One possible plot could be that a group of gladiators from the Spartacus era are somehow transported to the Star Wars universe. Maybe they end up on a planet like Tatooine. The gladiators' combat skills would be highly valued in the Star Wars underworld. They could get involved in the local power struggles, perhaps siding with the Rebels against the Empire as they are used to fighting for freedom in their own time.
One possible plot could be that Naruto and his friends are somehow transported to the Star Wars universe. Naruto, with his strong sense of justice, might join the Jedi Order. He could use his chakra abilities in combination with the Force. For example, his Shadow Clone Jutsu could be used to create distractions during battles against the Sith. His rasengan could be powered up with the Force for more destructive power.