Another plot idea is that Rex is wrongly accused of a crime within the guild. He has to prove his innocence while also dealing with a mysterious enemy that is secretly framing him. This could lead to a lot of character development as he tries to regain the trust of his friends.
One idea could be that Rex discovers a hidden power within Fairy Tail that was long forgotten. This power could be related to an ancient magic that only he can unlock due to his unique connection with the guild.
Maybe Rex gets involved in a time - traveling adventure within the Fairy Tail universe. He could go back in time to witness the founding of the guild and accidentally change something, leading to a whole new set of challenges for him and the guild members to fix.
One idea could be that Rex and Breach are forced to team up against a new, powerful EVO that threatens their mutual interests. Along the way, they start to understand each other's pasts and develop a grudging respect. For example, Rex could learn about Breach's difficult upbringing in the Nanite Collective and start to see her in a new light.
Another plot could be that an interdimensional rift opens up, and it's causing chaos in both Ben's and Rex's worlds. They discover that the source of the rift is related to the technology of both the Omnitrix and the Nanites. Together, they journey through the rift to find the cause and close it. Along the way, they meet alternate versions of themselves and their friends, which adds an interesting twist to the story.
One idea could be that Ben and Rex have to team up to stop a new villain who has the ability to disrupt both Omnitrix - based powers and Rex's nanites. They start off not trusting each other but as they face challenges, they learn to work together.
A plot idea could be that a powerful organization is stealing both biotech from Generator Rex's world and quirks from My Hero Academia's world. Rex and the heroes have to team up to stop them. Another idea is that Rex accidentally gets transported to the My Hero Academia universe and has to figure out how to get back while also dealing with the chaos of a world full of quirks.
One plot idea could be that Rex's nanites start to interact strangely with the eezo in the Mass Effect universe. This causes unforeseen effects like creating new forms of biotics or causing glitches in mass relays. Another idea is that Rex is mistaken for a new species and is studied by Cerberus, who want to use his nanites for their own evil purposes. He has to escape and team up with Shepard to take down Cerberus once and for all.
A possible plot could be that the Black Knight is wrongly accused of a crime. Rex and Generator Rex are initially tasked with capturing him. But as they get to know him during the chase, they realize he is innocent. So, they join forces to find the real culprit who is actually a powerful and corrupt figure trying to frame the Black Knight to gain more power in the post - apocalyptic world.
Rex could also be given a long - term goal, like mastering a very difficult form of magic. His journey to achieve this goal would involve a lot of trial and error, self - discovery, and training. Along the way, he would meet new characters who would either help or hinder him, which would further shape his character.
One idea could be a new character arriving at Fairy Hills and having to adapt to the unique living situation. They could face challenges like getting along with the different personalities of the Fairy Tail mages living there.
Another story could be set in a post - apocalyptic world where vampires have emerged as a result of some mutagenic event related to the nanites. Rex, being the only one with the ability to control his nanites, has to find a way to coexist with the vampires. He could encounter a vampire who was once a scientist and together they try to reverse the vampiric transformation in some people.
One idea could be a crossover where Generator Rex's nanites interact with the X - Men's mutant powers in unexpected ways. Maybe the nanites start to adapt and mimic some of the mutant abilities, causing chaos and confusion among both groups.