One possible plotline could be Ash discovering his heritage as the prince of aura and having to learn how to control and use his new - found powers. For example, he might struggle at first but then gradually master them to face stronger opponents.
One possible plotline could be Ash discovers his latent Aura Guardian abilities gradually. He might start having strange visions or experiences related to aura. Then, he has to find someone to train him, like an old Aura Guardian who has been in hiding.
One major theme is identity. The ash aura sets the prince apart, and often in these fanfictions, he has to figure out how it defines him, whether it makes him a hero or an outcast. Another theme is loyalty. The prince may have to deal with friends and allies who are either drawn to or repelled by his ash aura, and he has to figure out who is truly loyal. Also, the theme of destiny often comes up, as the ash aura may be a sign of a grander purpose for the prince.
One great aspect of Aura Guardian Ash fanfiction could be the exploration of Ash's latent aura powers. Maybe in these stories, Ash discovers he has a much deeper connection to the aura realm than he ever knew. This could lead to him having new abilities and forming unique bonds with Pokémon that are also attuned to the aura.
A plotline might involve Ash being betrayed by a new acquaintance he meets on his journey. This person could pretend to be his friend, gain his trust, and then use that trust to steal his Pokémon or important items. Or perhaps Ash is betrayed by a Pokémon he just caught. The Pokémon could have been planted by an enemy trainer to spy on Ash and then turn on him at a crucial moment.
A possible plotline could be that Fennekin is a rare and special Fennekin that only appears in a certain region. Ash hears about it and goes on a quest to find it. After a long search, he finally encounters Fennekin. Through a series of events, like helping Fennekin out of a dangerous situation, he earns Fennekin's trust and catches it.
One possible plotline could be that Ash is raised by Arceus to be a sort of Pokémon messiah. He is taught the true essence of Pokémon and is sent on a quest to save the Pokémon world from an impending doom.
Another plotline might involve Ash teaming up with some of the Team Rocket members, perhaps reluctantly at first. They could be forced to work together due to a common threat to both the good guys and the bad guys in the Pokemon universe. This would lead to some interesting character developments for Ash as he has to deal with the not - so - good nature of Team Rocket.
One possible plotline could be that Ash captures Suicune in an unexpected way, like during a special event in a new region. Then he has to deal with the consequences of having such a powerful and rare Pokémon, like other trainers being jealous or wanting to challenge him for it.
A common plotline could be Ash training Garchomp to become stronger for a big Pokémon league. He might face various challenges during the training process, like finding the right moves and strategies for Garchomp.
Another plot could be that Arceus is in some sort of trouble and Ash is the only one who can save it by capturing it. This could involve a complex story where Ash has to figure out what's wrong with Arceus and how to use his skills to capture it in a way that helps it.