In some Omnitrix fanfiction, there are crossovers with other universes. For instance, a story where the Omnitrix wielder ends up in the Star Wars universe. They have to use their alien forms to survive in this new and very different environment, facing off against Sith Lords and using their powers in creative ways to interact with the Force.
One interesting concept could be how the Omnitrix interacts with the unique chakra system in Naruto. Maybe it could transform the user into Naruto characters with added alien abilities from the Omnitrix. For example, turning into Naruto with the powers of Heatblast, allowing for a super - charged Rasengan with fire - based attacks.
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.
One idea could be a story where the Omnitrix is fused with a Pokeball, allowing the protagonist to transform into a Pokemon and use its powers while also being able to capture other Pokemon in a unique way. Another could be a cross - over where characters from Ben 10 (where the Omnitrix is from) end up in the Pokemon world and have to use the Omnitrix to survive and understand the new environment. A third idea is a story where a Pokemon trainer discovers an ancient Omnitrix - like device that gives them the ability to transform into rare and powerful Pokemon forms that no one has ever seen before.
One interesting storyline could be about Ben exploring new alien forms that were previously unknown in the official series. Maybe he discovers a form that has unique powers that he has to learn to control quickly to face a new and powerful enemy.
In 'naruto omnitrix bloodline fanfiction', a cool concept might be the exploration of different bloodlines through the Omnitrix. Maybe a character discovers a way to unlock hidden bloodline traits within the forms available in the Omnitrix that are related to Naruto's world. This could open up new storylines about heritage and power.
One possible interesting plot could be Harry using the Omnitrix to transform into various alien forms to battle dark wizards. For example, he might turn into a strong and durable alien to withstand powerful spells. Another plot could involve Harry trying to keep the Omnitrix a secret from his Hogwarts friends while still using it to his advantage in dangerous situations.
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.
One interesting concept could be exploring new alien forms that the Omnitrix can transform into. Maybe there are some hidden or rare aliens that Ben discovers in the fanfiction.
One idea could be that the Omnitrix malfunctions and gives Ben new, unexpected alien forms with powers he has to quickly learn to control. For example, an alien that can manipulate time in small bursts, which would create really cool scenarios where he has to fix things that went wrong in the past few seconds. Another idea is that a new villain is specifically targeting the Omnitrix and Ben has to protect it while also trying to figure out the villain's motives. Maybe this villain has a device that can nullify the Omnitrix's powers temporarily.
One idea could be that Ben discovers a new and powerful alien form in the Omnitrix that has abilities he's never seen before. He has to quickly learn to control it to defeat a new and dangerous villain.