How about a story where they have to train new demigods? They could share their knowledge and experiences, with Percy teaching combat skills he learned from Camp Half - Blood and Reyna sharing her Roman strategies. This would be a positive and engaging story that focuses on their characters in a proper way.
You could write about their adventures together. For example, they could go on a quest to retrieve a powerful artifact that was lost long ago. This would show their skills as demigods and how they work as a team.
A great topic would be their relationship development from a more emotional and psychological perspective. How they communicate their feelings, deal with their differences, and grow as a couple without involving sexual content.
A great topic could be their adventures together. For example, exploring a new, uncharted area in their world and how they work as a team to overcome obstacles. This would stay true to their relationship in the original story as comrades and friends.
A great topic could be how they help each other grow as individuals. Maybe Gwen helps Ben understand his powers better, or Ben teaches Gwen some self - defense skills. It would be a story about friendship and mutual improvement.
They could be involved in an adventure together where Aphrodite's powers of charm and Percy's combat skills combine. Maybe they have to work together to rescue a group of mortals who have been trapped by a powerful and evil magical being. This would show their different strengths coming together for a good cause.
You could write about their adventures in the hospital. For example, how they work together to solve a difficult medical case. This would show their professional relationship and how they complement each other in their work.
Some good topics would be their role in a prophecy. Maybe there's a new prophecy that requires both of them to play a crucial part. They could be on a journey to figure out what the prophecy means and how to fulfill it. Another idea is a story about them being ambassadors between the two demigod camps, trying to bridge the gap between the Greek and Roman demigods. This would focus on their leadership skills and how they can bring the two groups together.
One great topic could be Percy and Annabeth's further adventures in different mythological realms. For example, they could go on a quest to a less - known part of the Underworld to rescue a lost hero. Another idea is to write about their training new demigods at Camp Half - Blood. They could share their experiences and skills with the new recruits.
They could focus on their mentorship relationship. For example, Clary learning important skills from Luke like how to handle different magical situations or how to understand the world of shadowhunters better. This would be a positive and character - building exploration.
Their leadership skills would be an interesting theme. How they lead their respective groups and come together to lead in a joint mission. This can show their growth and development as leaders.
You could write about their adventures together, like exploring new planets or solving mysteries in the Star Wars universe.