Yes, there are. For example, some rom hacks add new regions, characters, and plotlines. You can find them on various rom hacking forums. Just be sure to check the legality and safety of using such hacks in your area.
One common theme is adventure. Since they are in the Pokemon world of ORAS, they often go on journeys together, exploring new regions and catching new Pokemon.
One common theme is their adventure. Fans often write about May and Brendan going on new quests in the Hoenn region, encountering rare Pokemon and facing new challenges.
Perhaps a fanfic where May and Brendan are chosen to participate in a special tournament in the ORAS region. But there's a catch - they have to train a Pokemon that they are not familiar with. This forces them to step out of their comfort zones and develop new training techniques. Along the way, they also deal with the pressure of the tournament and the expectations of their fans.
For May, you could develop her character by showing her struggle with more complex Pokemon battles. Maybe she has to face a series of tough opponents that make her question her training methods. For Brendan, he could be developed by having him interact more with different types of Pokemon, learning about their unique behaviors and needs.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. They have a large collection of Pokemon fanfictions, including those featuring May and Brendan from Pokemon ORAS.
One interesting Pokemon Steven fanfiction could be about his adventures in a new, uncharted region. He might discover rare Pokemon and form unique bonds with them. Another could be a story where he teams up with other trainers to face a powerful, mysterious threat to the Pokemon world.
May could be the protagonist who is on a journey to become the best Pokemon coordinator. Steven, on the other hand, could be a mentor figure. He could offer her advice on Pokemon training and evolution, which would be useful for her contests. For example, he might tell her about the special properties of certain stones that can enhance a Pokemon's abilities.
Another good opponent could be a character like Naruto from Naruto. Their powers are very different. Naruto has his ninjutsu and chakra, while Steven has his gem abilities. The clash of their ideals and fighting styles would make for a great fanfiction Death Battle.