I'm not entirely sure. Fanfic communities are vast and diverse. While it's possible that someone has written a fanfic with this concept, it could also be quite rare. It really depends on the creativity and interests of the fanfic writers within the Lelouch - related fandom.
C.C. is often a main character that interacts with Lelouch. Their relationship is complex and in the fanfic, they might continue to explore their connection, whether it's about the Geass or their personal feelings. Suzaku also could be a key character. He might have to come to terms with Lelouch being alive and they could either become allies again or have a more strained relationship.
One great 'lelouch x suzaku fanfic' is 'The Bond Beyond the Throne'. It delves deep into their complex relationship, exploring how their different ideologies still draw them together. It has some really well - written emotional scenes that show their mutual understanding and the unspoken bond between them.
Some dedicated Code Geass forums might also be a good source. Fans often share their own written 'lelouch fanfic' on these forums. Reddit can also be useful. There are sub -reddits related to Code Geass where people might post or recommend 'lelouch fanfic'. Just make sure to follow the rules of each platform when searching.
There are 'lelouch fanfic' stories that rewrite the ending. Maybe in these fanfics, Lelouch doesn't die at the end. Instead, he manages to find a way to create a new world order without sacrificing himself. Some fanfics also focus on the interactions between Lelouch and the other characters from different perspectives, such as his relationship with Suzaku as if they had made different choices earlier in the story.
Another aspect is the psychological aspect. Since both characters are complex, fanfics usually dig into their minds. They might show how Schneizel's calm and calculating nature contrasts with Lelouch's more passionate and impulsive side. This contrast can create a lot of interesting scenarios and internal conflicts within the story.
I highly doubt it. Given the disturbing nature of the theme (if it involves rape as the title suggests), it's not likely to be popular among the general audience who prefer positive and ethical content.
Since the idea involves such a disturbing concept as rape, it should not be promoted. Fanfics are supposed to be creative works within the boundaries of legality and morality. There's no value in exploring the details of this kind of 'fanfic'.
One common theme is the exploration of their complex relationship. They have a deep connection in the original series, and fanfics often expand on it, like delving into their trust issues. Another theme is the power dynamics between them, as CC has her own powers and Lelouch has his Geass.