I doubt it. The name seems so strange and unappealing that it's probably not very popular. Most popular Pokemon fanfics usually focus on more mainstream ideas like Ash's adventures, his battles, or his relationships in a more typical Pokemon - like way.
One key element could be Ash's character development. In such fanfictions, he might face new and tougher challenges that push him to grow even more as a trainer. Another element could be the introduction of rare or new Pokemon species. It would be exciting to see Ash interact with Pokemon we haven't seen him with in the original series. Also, his relationships with his friends, like Misty and Brock, might be explored in new and deeper ways, adding more emotional depth to the story.
Pikachu is a very likely candidate. It's Ash's most iconic Pokemon and has a deep bond with him. Whenever Ash is in trouble, Pikachu often steps up to protect him.
In Si as Ash Pokemon fanfiction, a prevalent plot is Si being a rival to Ash at first but then becoming his closest ally. They could compete in Pokemon battles and then team up against a greater threat, like an evil organization trying to capture all the rare Pokemon. There might also be a plot where Si discovers a hidden power within Ash that even Ash himself doesn't know about, and they work together to harness that power for the good of the Pokemon world.
One interesting plot could be that Ash discovers Mew while on one of his adventures. Mew, being curious about Ash, starts to follow him around. As time passes, they form a special bond that is different from Ash's relationships with his other Pokémon. Ash helps Mew understand the human world better, and in return, Mew uses its unique powers to assist Ash in his battles in unexpected ways.
One popular theme is their journey together. They might go on adventures in different regions, facing new Pokemon and challenges. Another theme could be their friendship development. It could show how they support each other through tough times. Also, a common theme is their rivalry. They might compete in Pokemon battles, which can be really exciting to read about.
One popular theme could be Ash and Trip's adventures together. They might face powerful Pokemon and form a deeper bond through those experiences. Another theme could be their rivalry evolving into a strong friendship as they learn from each other's skills and strategies.
One interesting plot could be that Ash discovers a new Pokemon that has the power to make things around it gain weight, and accidentally gets affected himself. This leads to him having to adapt to his new body while still trying to pursue his Pokemon journey.
Ash could be a Pokémon trainer with a different starting point in this fanfiction. Born in 1987, by 1997 he might have already made a name for himself in local Pokémon battles. He could have a team of Pokémon that he rescued from difficult situations, like a Charmander that was abandoned by its trainer. His story could revolve around giving these Pokémon a second chance and proving that Pokémon don't need to be 'perfect' to be strong.
The impact of Ash's loss in the fanfiction could extend beyond just himself. His Pokémon might also feel demoralized. However, this could also be an opportunity for them to grow stronger together. Ash could start training more intensively, seek new training methods, or even try to catch new Pokémon to strengthen his team.