One plot idea could be Ash and Red teaming up to face a new, extremely powerful and mysterious Pokemon. They would have to combine their unique skills and knowledge of different Pokemon regions.
Well, a great plot idea might be that Red and Ash find a mysterious Pokemon that has powers neither of them have ever seen. They have to work together to figure out how to care for it and also protect it from an evil organization that wants to use its power for bad. Maybe they also learn some new training techniques from each other along the way.
One idea could be Ash getting transported into the world of Pokemon Red. He could meet the original Red and they team up to face a new, powerful villain. Maybe a mysterious Pokemon that has powers beyond any they've seen before.
A great plot could involve Ash and Red exploring the mysteries of the Kalos region. They discover ancient Pokémon secrets or a hidden power that threatens the balance of the region. Together, they embark on a journey to find a way to stop this threat, facing various obstacles and making new friends along the way. This would not only showcase their courage but also their ability to work together.
In some fanfictions, Ash and Red might have a friendly rivalry. For example, they could hold a series of Pokemon battles across different terrains to see who is the better trainer. This could involve a lot of training montages for their Pokemon, strategizing about type advantages, and some really exciting battle scenes.
One idea could be that Ash and Maya embark on a journey to find a rare and powerful Pokemon that is said to be able to control the weather. Along the way, they face challenges from a team of villains who also want the Pokemon for their own evil purposes.
One interesting plot idea could be Ash getting lost in Sabrina's psychic maze and having to rely on his Pokémon's instincts more than his own. Another could be Sabrina having a premonition about Ash's future battles and deciding to train him in psychic - type moves. Or perhaps there's a Pokémon that is causing chaos in the town and Sabrina and Ash have to team up to stop it, which also helps Sabrina to open up more and become less aloof.
One interesting plot idea could be Ash and Dawn teaming up to explore a new, uncharted region in the Pokemon world. They could encounter rare and unique Pokemon species that are not known to the rest of the world. Another idea is that they participate in a special tournament where the rules are very different from the regular Pokemon battles, like battles on floating platforms or with certain type restrictions. A third plot could be that they discover a mystery related to an ancient Pokemon civilization and have to solve it to save the present - day Pokemon world from some kind of threat.
One idea could be that Ash and Latias team up to save a group of Pokémon from an evil organization. Ash uses his battle skills and Latias uses her psychic powers.
One idea could be that Ash and Manaphy go on a journey to find a rare type of Pokemon food that can heal all Pokemon. Another could be that Manaphy gets lost and Ash has to traverse through a dangerous forest to find it. Or perhaps they team up to save a group of Pokemon from an evil trainer.
A more complex plot could be set in a world where there is a threat to all Pokemon. Ash and Astrid, along with their Pokemon friends, have to gather a set of ancient artifacts to save the Pokemon world. Along the journey, they have to overcome their own personal doubts and differences to succeed.