Well, in such a fanfiction, the plot might involve Team Rocket devising a clever plan to capture Dawn. Maybe they use some new and devious Pokémon or traps. They could be after her Pokémon for some evil scheme, like using them to take over a Pokémon Contest Hall.
Obviously, Dawn and the members of Team Rocket like Jessie, James, and Meowth are the main ones. But there could also be Dawn's Pokémon, like Piplup, which might try to rescue her. And there could be other Pokémon trainers or characters from the Pokémon world who might get involved in the rescue mission.
Well, it could make for a really interesting fanfiction. Dawn joining Team Rocket would change the whole dynamic. Her Pokémon might not be too happy about it at first. She could bring new ideas to Team Rocket, since she has a different way of thinking compared to Jessie, James and Meowth. However, it's also possible that she would secretly be working against Team Rocket from the inside, trying to take them down while pretending to be one of them.
One possible storyline is that Dawn joins Team Rocket thinking it's a legitimate Pokémon training organization at first. But as she gets deeper into it, she discovers their true evil nature. Another could be that she is brainwashed by Team Rocket into joining them. Her friends then have to find a way to break the brainwashing. A third storyline could be that she joins willingly because she has some sort of vendetta against the Pokémon League and sees Team Rocket as a way to get revenge.
Maybe there's a rogue Pokemon trainer. This trainer is jealous of Dawn's skills and the attention she gets. When Dawn joins Team Rocket, this trainer sees it as a chance to expose her as a fraud. He or she then tries to stop Dawn and Team Rocket's activities, thinking that they are up to no good, which they are, but the trainer has his own self - centered motives.
One possible plot could be that Dawn, for some reason, gets disillusioned with her regular Pokemon journey. Maybe she has a series of losses that make her question her methods. Team Rocket, seeing an opportunity, convinces her that they have a better way to train and use Pokemon. She then joins them, initially helping with their small-time schemes, but gradually realizes that their actions are unethical and has to find a way to break free.
Team Rocket and Team Plasma have some interesting differences. Team Rocket is more about classic criminal activities like stealing Pokémon for profit. In fanfiction, they often clash with trainers in a more straightforward, greedy way. Team Plasma, on the other hand, has the ideology of 'liberating' Pokémon, which can lead to complex storylines. In many fanfictions, their clash is not just about power but also about different views on Pokémon-human relationships.
If Team Rocket turns Ash into a Pokemon, it could lead to a really interesting story. Ash would have to experience the world from a Pokemon's perspective. He'd understand their struggles, like being caught and trained. This could also be a way for him to better understand his own Pokemon and their bond with him. And it would be a wild adventure as he tries to find a way to turn back to his human form.
In a fanfiction where Ash joins Team Rocket, it could lead to some really interesting storylines. Ash has a lot of knowledge about Pokémon training that Team Rocket lacks. He could potentially teach them new techniques, but at the same time, his moral compass would be constantly at odds with their devious ways. Maybe he joins them because he's somehow tricked or he has his own secret plan to take them down from the inside. It would be a great opportunity to explore different aspects of his character and how he adapts to this new situation.
The fanfiction could start with Dawn being in a vulnerable situation, perhaps alone in an area where Team Rocket has set a trap. Ash, who has a sense of justice and cares about Dawn, discovers the situation. He then uses his knowledge of Pokémon battling, combined with his quick thinking, to outwit Team Rocket. His Pokémon work together as a team, and through a series of exciting battles and maneuvers, he manages to rescue Dawn from the clutches of Team Rocket.