In some fanfictions, there might be female versions of some of the alien species that are popular in the Ben 10 universe. These female alien characters with their own Omnitrix - like devices could be popular. For example, a female Heatblast or a female Four Arms. Their unique abilities and personalities would attract readers, and the stories could explore how they use their powers in different situations compared to their male counterparts.
Then there's Lyra. She's a female OC who is a brilliant scientist. She reverse - engineers some of the Omnitrix's functions and creates her own power - enhancing devices. She often teams up with other OCs and uses her intelligence along with the Omnitrix's powers to outwit their enemies.
Another could be an OC with the Omnitrix getting stuck in a parallel universe where the rules of the Omnitrix are different. For example, instead of being able to transform into known aliens, the OC has to figure out how to use new and strange alien forms that are native to that universe. This could lead to all sorts of adventures as the OC tries to find a way back home.
Some fanfictions might explore the idea of a Fem Omnitrix having unique features. For instance, it could have an enhanced ability to transform into female - only alien species. This could lead to new adventures and storylines. Additionally, the fanfiction could focus on how the female character's identity is affected by having the Omnitrix. She might struggle with the power and responsibility in a different way than Ben, which would add depth to the story.
You could also write a fanfiction where an OC is accidentally bonded with the Omnitrix in a way that it can't be removed. The OC then has to learn to live with it and use its powers for good, but they face challenges as they are not Ben. They might have to deal with people who are suspicious of them having the Omnitrix and also face enemies who are specifically after the device because of its new and unexpected host.
He could have a unique personality trait, like being extremely shy but when he transforms using the Omnitrix, he becomes super confident. For example, if he transforms into a big, strong alien, his normal timid self disappears and he becomes a fearless leader in battle.
To create a unique male OC, consider his appearance. He could have a unique scar or birthmark that has a special meaning related to the Omnitrix. Also, think about his skills and knowledge. He might be a genius when it comes to technology because he has spent so much time trying to understand the Omnitrix. His relationships are important too. He could have a mentor figure who is an old alien that he met during one of his early transformations.
Maybe the male OC is from a different dimension where the Omnitrix works in a completely different way. He accidentally gets transported to the Ben 10 universe. His Omnitrix has some unique alien forms that are not known in this universe. He teams up with Ben and Gwen to fight a new common enemy that is attracted to the strange energy his Omnitrix emits. Along the way, he learns about the values of friendship and courage from them.
One idea could be that the male OC with the Omnitrix accidentally gets transported to an alternate dimension where the Omnitrix functions differently. He has to figure out how to adapt and use it to get back home. Another plot could involve the OC using the Omnitrix to stop an alien invasion that is targeting his hometown specifically. Maybe the aliens are after the Omnitrix's power source.
Well, for example, Natsu's fire - dragon slayer magic could potentially interact with a heat - based alien form from the Omnitrix. Maybe when he's in that form, his fire magic becomes even more intense or has a different quality to it. He could use his dragon slayer skills to control the heat in a more precise way than the alien form normally allows.