Another possibility is Heimdall. As the all - seeing guardian of the Bifrost, he would be aware of Odin's situation from the start. He could be the one trying to piece together what happened to Odin and prevent any disasters that might occur as a result of Odin's wipe. His unique abilities and loyalty to Asgard would make him a strong candidate for the main character.
One possibility is that it could focus on a mentoring aspect. Old Kratos, with all his wisdom and experience, could guide young Kratos. Maybe he'd show him different combat techniques or how to better control his rage. It could also be a story of self - discovery for young Kratos as he sees his future self and realizes the potential path he could take.
One possible plot could be that Percy is a young warrior who looks up to Kratos. He sets out on a journey to find Kratos and learn from him. Along the way, he faces many challenges similar to those Kratos has faced in the God of War series. Maybe he has to battle mythical creatures and overcome his own inner demons, all while hoping to one day be as great as Kratos.
It could be a story where Naruto, inspired by Kratos' strength and tenacity, decides to train in a similar way. Maybe he takes on some of Kratos' combat styles and uses them in the Naruto universe, like using his chains to grapple enemies just like Kratos' Blades of Chaos.
The plot of a Kratos and Aphrodite fanfic could center around Aphrodite falling in love with Kratos at first sight. She tries to win his heart by using her beauty and allure. But Kratos is oblivious to her advances as he is preoccupied with his own past traumas. As she persists, he starts to open up to her, and they form an unlikely bond. This bond then becomes the foundation for them to face a common enemy that threatens both their worlds.
Well, it could be that Naruto somehow gets transported to the world where Odin exists and is mistaken for a powerful being like Odin. Maybe he has to take on Odin - like responsibilities and use his Naruto - skills in a new and strange setting.
In this fanfiction, the mother could be a powerful sorceress. She used her magic to create a baby with Kratos' essence for some grand purpose. But then she disappeared, leaving Kratos to deal with the baby. This would add an interesting layer of mystery to the story as Kratos tries to figure out why she did it and what the baby's true nature and purpose are.
An 'Avengers meets Kratos' fanfiction could be really interesting. Kratos has his own set of moral codes which could clash or align with the Avengers'. Captain America might try to understand Kratos' motives and see if he can be trusted. Black Widow could use her skills to spy on Kratos initially to assess the threat level. And then, as the story progresses, they could find common ground in protecting the world or the universe from a greater evil.
The story could focus on the challenges they face. Maybe there are shortages of food or supplies in their area, and Kratos has to go on dangerous quests to get what Faye needs during her pregnancy. It would test his skills and his love for his family.