It could be a Pokemon trainer who has a special connection with a particular Pokemon. This trainer gets recruited for an experiment because their Pokemon has shown some unique abilities. The trainer then has to balance their normal training routine with the demands of the experiment, all while protecting their beloved Pokemon from any potential harm that the experiment might bring.
Perhaps a powerful and mysterious trainer. This trainer is jealous of Ash's connection with his Pokemon and his ability to conduct these experiments. He wants to prove that he is the better trainer. So he tries to disrupt Ash's experiments by challenging him to battles at inconvenient times. He also spreads false rumors about Ash's experiments being dangerous to other Pokemon, which causes some local Pokemon communities to be hostile towards Ash.
It could be a professional Pokemon groomer. They are known all over the region for their amazing skills in giving Pokemon haircuts. They have a special bond with each Pokemon they groom, and they often get requests from famous trainers.
The main character could be a young and ambitious Pokemon scientist named Professor Willow. He has just graduated from the Pokemon Research Academy and is eager to make a name for himself in the scientific community. He specializes in studying the behavior of electric - type Pokemon.
A half - vampire, half - human character would be really interesting. They would have the strength and some of the powers of a vampire, but also the connection to the human world of Pokemon training. They could be on a quest to find their place in the world, whether it's among the humans, the vampires, or with the Pokemon themselves. They might face discrimination from all sides, but also find unique ways to use their abilities to their advantage in Pokemon battles.
A less obvious choice could be Team Rocket's Jessie. She has been around Pokémon a lot, even if in not - so - ethical ways at first. But she could have a change of heart and use her knowledge of the Pokémon underworld to clean up any illegal Pokémon trading and fighting rings as president.
A Totodile might be the main character. Totodile is a bit mischievous. It could use its big jaws to grab onto opponents and its energetic nature to perform wild and unpredictable wrestling maneuvers. Plus, its evolution into a Feraligatr could be a major part of its character arc in the fanfic as it becomes an even more formidable wrestler.
Perhaps a story where a mad scientist is conducting cruel Pokemon experiments in a secret lair. His goal is to create the ultimate fighting Pokemon by using unethical methods. A young and brave Pokemon trainer gets wind of this and decides to put a stop to it. The trainer has to battle through various mutated and tortured Pokemon created by the experiment before facing the mad scientist himself.
Maybe an experienced trainer who has heard rumors about a haunted house and decides to investigate. This trainer would be confident in their abilities and their Pokemon's strength. They might be on a quest to discover rare Pokemon that are rumored to be in the haunted house or to prove that there's nothing to be afraid of. However, they soon find out that the hauntings are real and more dangerous than they thought.
It could be a young and curious Pokemon researcher. This person is fascinated by the idea of creating Genesect and devotes all their time to studying the necessary genetics. They might be a bit of an outcast in the scientific community because their ideas are so radical.
Perhaps a scientist who has been studying Pokemon for years. When Pokemon start to rule the world, this scientist uses their knowledge to figure out how to live in this new situation. They might try to find a way to reverse the situation, or at least make sure that humans are treated fairly under Pokemon rule.