A really cool 'Ben 10 Star Wars fanfiction' idea could be that there is a planet in the Star Wars universe that has a natural phenomenon similar to the Omnitrix. Ben discovers this planet and teams up with local characters. They find out that an evil Sith Lord also wants to use this phenomenon for his own evil purposes. Ben has to use his experience with the Omnitrix and his alien forms to stop the Sith Lord and protect the planet and its people.
Well, you could have a fanfiction where the Galactic Empire somehow gets hold of the Omnitrix. Then they try to use it to create super - soldiers. Ben, of course, has to break into their strongholds to get it back. Or perhaps there's a story where Ben is mistaken for a new type of Force - user because his alien transformations seem to give him powers similar to the Force in some ways. He then has to navigate the complex politics of the Star Wars galaxy while trying to clear his name.
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 interesting idea could be exploring Ben's internal struggle in more depth. Maybe his journey to fully embrace the light side and overcome the dark influences that have been plaguing him. It could also involve new relationships he forms during this awakening process, like with characters who help him see a different path.
One common plot idea is Ben Skywalker's training. Fanfictions might explore his journey to become a powerful Jedi, facing various challenges and learning from different masters. It could include his struggle with the dark side, similar to what his father, Luke Skywalker, faced.
One interesting crossover could be Ben using his Omnitrix to transform into an alien that has Jedi - like powers. For example, a species with enhanced mental abilities similar to using the Force. Another could be a scenario where the villains from Ben 10 team up with the Sith in Star Wars to take over both universes. Maybe Vilgax and Darth Vader working together, with Vilgax's brute strength and Vader's mastery of the dark side of the Force creating a really formidable alliance.
One interesting crossover could be Ben using his Omnitrix to transform into an alien that has the power to use the Force. For example, he could transform into a species that has telekinetic abilities similar to Jedi powers. Another could be the Ben 10 characters getting involved in the Galactic Civil War in the Star Wars universe. Maybe they help the Rebels fight against the Empire using their unique abilities.
One idea could be Ben using his Omnitrix to transform into an alien form that has a special ability to counter the Force. For example, a form that can disrupt the connection between a Jedi and the Force. Another plot could involve Ben and the Star Wars characters teaming up to fight a common enemy like a new Sith lord who has some sort of technology that can nullify the powers of the Omnitrix. Or perhaps Ben gets lost in the Star Wars galaxy and has to use his wits and the powers of the Omnitrix to find his way back home while getting involved in local conflicts.
One idea could be exploring the backstory of a minor character in Star Wars 1. For example, a young Padawan who was on the same Jedi training grounds as Anakin but had a very different path. Another could be a fanfiction that focuses on the political intrigue on Naboo before the Trade Federation blockade. Maybe there were some secret meetings or power plays that we didn't see in the movie. A third idea is to write a story from the perspective of a droid during the events of Star Wars 1, like how they experienced the chaos and battles.
Perhaps a fanfiction where a group of gamers create their own custom clone units in the game and then those units somehow become real in the Star Wars universe. They then have to train and lead these unique clones in battles.
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.
Definitely Ben Tennyson himself. His ability to transform into various aliens would add a whole new dynamic to the Star Wars universe. Also, characters like Darth Vader would be great. Imagine the confrontation between Ben in one of his powerful alien forms and Vader with his lightsaber and the Force. Another interesting character could be Yoda. Yoda's wisdom and his unique view of the Force could interact in an interesting way with Ben's more action - based alien powers.