It could be a new trainer who just started their journey and is determined to make a name for themselves in the Champion League. For example, a young girl from Pallet Town who has big dreams.
An older trainer who has had many setbacks in their Pokemon training career but is making one last attempt at the Champion League. Maybe someone who has lost in previous leagues and is now more experienced and wiser. They could have a team of Pokemon that they've carefully nurtured over the years.
The main character could also be a local Alola resident who has a special connection with the land and its pokemon. They grow up hearing stories about the champion and dream of one day achieving that status. Their understanding of the local environment and pokemon gives them an edge in their journey to become the Alola champion.
It could be an underdog trainer who has been training hard in the shadows and finally gets the chance to participate in this exclusive event.
Maybe an underdog trainer who has been training in secret and decides to enter the 'champion of champions' competition to prove themselves. This character could have a unique bond with their Pokemon that gives them an edge in battles.
Perhaps there's a dark - horse candidate, a relatively unknown trainer who has been quietly training and is now ready to take on Ash in the Champion League. This trainer could have some unorthodox training methods that make their Pokémon very difficult to defeat. And then there are always the regular tough competitors that Ash has faced in previous leagues, some of whom might also be in the Champion League in this fanfiction.
Typically, the young and upcoming trainers are the ones most affected. They have to quickly adapt to the new rules and changes in the Pokemon League. For instance, a novice trainer who was just getting used to the old battle format now has to learn a new one.
The main character could be a young Gringotts trainee who has always been overlooked but has a hidden talent for magic related to the vaults. Maybe they can sense the magical auras of different vaults and their contents, which is a rare ability. This character gets chosen as the champion unexpectedly and has to rise to the challenges that come their way, learning about their own power and the secrets of Gringotts along the way.
It could be Neville Longbottom. He has the potential to be a supreme champion. He grew a lot throughout the series, and in fanfiction, he could be given more opportunities to shine and show his true power and skills, becoming the supreme champion.
One idea could be a trainer from a small, unknown town who enters the Pokemon Champion League with an underdog team of Pokemon. Another could be a story about a former champion who comes back to reclaim their title after a long hiatus. Maybe a story where a trainer has to face unexpected challenges during the league, like a new type of Pokemon or a rule change.
It could be a scientist who is involved in the study of Pokemon genetics. While trying to understand the mechanics of evolution better, they accidentally stumble upon the new evolution and then become involved in the events that unfold as a result, both in the scientific and the trainer communities.
It could also be an experienced pokemon trainer who has seen a lot in their travels. After encountering a mirage pokemon by accident and realizing how different and powerful they are, they become determined to become the mastermind in the world of mirage pokemon. They use their existing pokemon training skills and knowledge to study these special pokemon, making them a formidable force in the fanfiction.