In some fanfictions, they might start as enemies as they were in the original series. But through time travel, they could gradually come to understand each other better. For instance, if they are forced to work together to fix the messed - up timelines, they would see the motives behind each other's actions more clearly.
Another plot could involve them traveling to a different timeline altogether. In this new timeline, they might find themselves in a world where the power of Geass doesn't exist. This would force them to rely on their wits and leadership skills in a completely different way. They could either try to find a way back to their original timeline or decide to make the best of the situation and change this new world for the better.
One interesting 'lelouch x clovis fanfiction' could be about their complex relationship in an alternate universe where they have to work together to save their kingdom. In this story, they might put aside their differences and learn to understand each other's motives.
You can start by looking on popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, and there's a good chance you'll find some great 'lelouch x clovis' ones there.
Character development is also key. The fanfic should develop both Clovis and Lelouch's characters further. Maybe show a different side of Clovis that we didn't see much in the anime, or explore Lelouch's reactions and thoughts in situations related to Clovis more deeply. It could also introduce new characters that interact well with them.
Another option is to check out some Code Geass - dedicated fan forums. Some of these forums have sections for fanfics. Members of the community often share their own works or recommend good fanfics they've read. You can ask around in the forum if anyone knows of a fanfic with Clovis and Lelouch in it.
Time travel can greatly expand Lelouch's character development. When he travels back in time, he gets a second chance. This makes him more cautious as he doesn't want to repeat the same mistakes. For example, he might be more careful in his relationships with Suzaku and others, knowing how things turned out before.
One possible fanfiction could involve Lelouch traveling back in time and trying to change his relationship with Cornelia Nonette. Maybe he uses his knowledge from the future to prevent certain events that led to their conflict. For example, he could try to find a way to make her understand his motives earlier in the story, which might lead to an alliance between them instead of enmity.
One great fem Lelouch time travel fanfiction is 'The Time - Traveling Empress'. It has an interesting plot where fem Lelouch uses her knowledge from the future to change the course of the story in a really engaging way.
One possible fanfiction could be where Lelouch time - travels back to a crucial moment in the story. With the help of Loyd's brilliant mind and Cecile's technical skills, they try to change the course of events for the better. Maybe they prevent a certain tragedy from occurring that originally had a huge impact on the story's development.