Another possible ending is that Gohan sacrifices himself to defeat Cell. He could use a self - destructive move that not only takes out Cell but also costs Gohan his life. This would be a very dramatic and tragic ending, but it would also show Gohan's selfless heroism.
Trunks could also be a popular character in such fanfictions. He might be curious about Gohan's interactions with Cell and get involved in their affairs. His time - traveling knowledge could add an interesting twist to the story. Also, Vegeta could be included. His pride might not allow him to accept Gohan getting too close to Cell and he could try to put an end to their relationship or partnership in the fanfiction.
One idea could be to focus on Gohan's internal struggle during the Cell Games. Maybe he's doubting his abilities even more than shown in the original, and it's through his friends' and family's words of encouragement that he finally finds his resolve.
Well, this fanfic could be quite interesting from a character - development perspective. If Cell kills Gohan, it could change the entire dynamic of the Dragon Ball world. For example, Vegeta might be forced to step up in a different way, or the Z - fighters might have to completely reevaluate their strategies. It might also show a different side of Cell, perhaps a more menacing and victorious side that we haven't fully seen in the original series.
In fanfiction, Gohan could have a secret power that he discovers during the Cell Games. This power could be related to his Saiyan heritage in a new and unexpected way, like being able to tap into an ancient Saiyan ability that no one else knew about. It could completely change the course of the fight against Cell.