Well, perhaps Ash could gain new and amazing powers. Shiny pokemon often have special abilities or appearances, so if Ash turns into one, he might be able to fly like a shiny bird - type pokemon or have super strength like a shiny fighting - type. He could also use his new form to communicate better with pokemon, since he'd be more like them.
It could be a jealous trainer. This trainer might see Ash in his shiny pokemon form and want that power for himself. So he tries to capture Ash by any means necessary, setting up all kinds of traps and challenges for Ash and his friends.
Well, it depends on the specific fanfiction. Some fanfiction authors might choose to give Ash shiny Pokemon as a way to show his growth or as a special encounter. For example, he could find a shiny Pikachu in a different region in one fanfic, which would then lead to a whole new set of adventures and challenges. It adds an element of surprise and rarity to the story.
Yes, in many Pokemon fanfictions, Ash might be depicted as having a shiny Pokemon. Shiny Pokemon are rare and having one would make for an interesting plot point in a fan - created story.
Obviously, Ash is one of the main characters. He is the trainer who catches the shiny Pokemon. His Pikachu also plays a significant role, as it's always by Ash's side and could potentially have some interesting interactions with the shiny Pokemon.
In this fanfiction, Ash could start in a mysterious forest and spot a shiny Celebi. Celebi, being a time - traveling Pokemon, could take Ash on a journey through different time periods in the Pokemon world. He might see how the Pokemon world has evolved over time, meet some of his ancestors or future versions of himself, and have to solve various problems in each time period to keep the balance of the Pokemon world.
Another possibility is Ash becoming Lugia. Lugia is known as the guardian of the seas. As Lugia, Ash could explore the deep oceans, discover new species of Pokemon, and safeguard the marine ecosystem. He could use his psychic and flying abilities to interact with both water - and flying - type Pokemon, bringing a new era of harmony between different Pokemon types.
Well, if Ash were to turn into Mew in a fanfiction, it would be quite a wild turn of events. Mew is known for its ability to transform and its vast psychic capabilities. Ash, with his new form, could potentially travel to different dimensions that were previously inaccessible. He could also communicate with Pokémon in a whole new way, using Mew's psychic powers to understand their deepest thoughts and feelings.
Well, if Ash turns into a Pikachu in a fanfiction, it would be quite a transformation. Firstly, his communication with Pikachu would become more of an internal dialogue. And he'd have to get used to moving around on all fours and using Pikachu - like movements. His battles would be completely different too. He'd be relying on Pikachu's natural skills rather than his own battle strategies as a human trainer.