In this fanfiction, perhaps Ash starts with a Eevee. Since Eevee can evolve into multiple forms, it would add a whole new dimension to his journey. He could face different challenges as he tries to decide which evolution path to take for Eevee, and it would also attract different kinds of Pokémon opponents.
The fanfiction might have Ash starting with a Growlithe. This would change his whole team dynamic. He'd have to deal with Growlithe's strong sense of loyalty and protectiveness from the start. Also, he might encounter different trainers who are interested in trading for his unique starter, which could lead to some interesting plot twists.
Another possibility is that an old rival of Ash's, who has always been jealous of his success, becomes the main antagonist in this fanfiction. When Ash chooses a different starter, this rival sees it as an opportunity to finally defeat him, thinking that Ash's new and untested starter will be his downfall.
If Ash had a different starter like Bulbasaur in fanfiction, his team composition would change significantly. He might focus more on grass - type Pokemon to complement Bulbasaur's abilities. His travels through different regions could be affected as well. Maybe he would be more drawn to areas with more plant - life where Bulbasaur could thrive. Also, his interactions with other trainers having fire - type starters would be more interesting due to type advantages and disadvantages.
A possible plot could be centered around the mystery of Latios. Since it's a very special Pokémon, there could be ancient secrets associated with it. Ash, with Latios as his starter, would be on a quest to uncover these secrets. Along the way, they would face other trainers who are envious of Ash having such a powerful Pokémon. Ash would have to prove that he is a worthy trainer of Latios through his skills and the bond they share.
One idea could be to have Ash start with a different type of Pokémon that is not commonly chosen in the main series, like a Skorupi. The story could revolve around the challenges he faces in training it as it has a somewhat menacing appearance and is a Poison - type, which might make some people in the Pokémon world a bit wary. This would lead to interesting interactions with other trainers and gym leaders.
Well, if it's 'Ash gets a different starter fanfiction', perhaps he gets a Bulbasaur as his starter. This would lead to him being more involved in grass - type Pokémon battles and strategies. He could end up exploring different regions in search of rare grass - type Pokémon to strengthen his team. Also, his personality might develop in a different way, as Bulbasaur has a calmer and more patient nature compared to some other starters, which could influence Ash's own temperament over time.
The plot could involve Ash and Chimchar facing a series of challenges in a new Pokémon league. They might encounter a powerful villain who has a special device that can nullify Chimchar's fire attacks. Ash then has to find a way to train Chimchar to use its other skills, like its speed and agility, to defeat the villain's Pokémon.
One possibility is that Ash discovers a young Rayquaza at the start of his journey. Maybe it's injured and Ash nurses it back to health. This could lead to a strong bond between them, and Rayquaza could become his most powerful Pokémon, helping him in battles against tough opponents like Team Rocket or other powerful trainers.
One interesting plot twist could be if Ash received a non - traditional starter like a shiny Pikachu as his starter. It would change the whole dynamic of his journey. Since Pikachu is already so strong and unique, it would make his early battles very different. He might not struggle as much in the beginning against the first gym leaders and could quickly gain a reputation as a powerful trainer with an unusual starter.
Well, it could start with Ash being in a new region where Treecko are very rare. He stumbles upon a young Treecko that is being bullied by other Pokémon. Ash steps in to protect it, and Treecko, seeing Ash's kindness, decides to join him. Their journey together focuses on exploring the unique ecosystems of this new region. Treecko has to adapt to new battle styles and opponents. Ash and Treecko also befriend a group of local Pokémon trainers who help them understand the secrets of the region. In the end, they face a powerful trainer who has a team full of strong Pokémon, and they have to use their combined skills and the knowledge they've gained to win the battle.
One possible plot could be that Ash discovers a Larvitar in a mysterious cave. The Larvitar is injured and Ash decides to take care of it. As they journey together, Larvitar starts to grow stronger and they face various challenges in Pokemon battles. Eventually, Larvitar evolves into Pupitar and then Tyranitar, becoming one of Ash's strongest Pokemon.