A major theme is the exploration of new powers. When Pokemon transform, they may gain new powers that they need to understand and control. Also, friendship is a common theme. The transformed Pokemon still rely on their friends, and these relationships are often explored in the fanfic.
Another idea is that the Pokemon have some of the abilities of the TF2 characters. So, there could be a Pikachu with the Scout's double - jump ability. Or a Snorlax that has the Heavy's strength and can use a 'Mini - Gun' - like attack which is actually just a powerful Tackle. This would create really unique and interesting battles.
You should also consider the rules of both universes. In the TF2 world, there are guns and different classes with unique abilities. In the Pokemon world, there are types, evolutions, and moves. Try to find a way to blend these rules in a logical way. For instance, the Spy could use his invisibility cloak to sneak up on Pokemon trainers, just like he does in TF2. And when it comes to writing the actual story, start with a strong hook to draw the reader in, like a big battle between a TF2 character and a powerful Pokemon right at the start.
In some fanfics, a human character might be transformed into a half - Pokemon, half - human hybrid. This often involves a complex exploration of identity. The character has to deal with not fully belonging to either the human or Pokemon world, and might go on a journey to find their place in this new state of being.
A possible plot could involve a Pokemon having some sort of connection to the technology in the TF3 world. Maybe a special Pokemon's power can enhance the soldier's weapons or armor. The soldier then has to protect this Pokemon from those who want to use it for evil. And along the way, he discovers new types of Pokemon and forms bonds with them.
Perhaps a legendary Pokemon could be the main character in a way. The TF3 soldier and other characters are all drawn into the story because of this Pokemon's actions or powers. The soldier might initially see it as a threat but later realizes it's a key to solving a greater mystery or problem that spans both the TF3 universe and the Pokemon world.
Some 'Ash Pokemon TF fanfic' stories focus on Ash being transformed due to a strange Pokemon ability or a magical item. In these, his new form often gives him new powers or challenges. He might have to learn how to use his Pokemon moves in his new body, which can lead to really interesting plot developments. For instance, if he becomes a Charizard, he'd have to deal with the power and temperament of that form.
You can start by looking on fanfic websites like FanFiction.net. There's a large collection of Pokemon - related fanfics there, and you're likely to find some 'Ash Pokemon TF fanfic' among them.
Sure. In these fanfictions, Ash's transformation can be due to different reasons. It could be a magical spell gone wrong, or some strange Pokemon power. One interesting aspect is how he uses his new form to battle or solve problems. Some fanfictions also delve into the emotional side of things, like how Ash feels about being in a different body and how he copes with the changes in his daily life.
Sure. 'A Pokemon's Transformation' is quite popular. It has an interesting plot where a Pikachu gradually transforms into different types of Pokemon due to a mysterious power. Another one is 'The TF Adventure of Eevee' which follows Eevee's journey of unexpected transformations.