Melisandre could be a very interesting female dominant character in a femdom story. She has her own brand of power with her magic and her influence over Stannis Baratheon in the original series. In a femdom context, she could use her allure and her powers to dominate male characters. Also, Brienne of Tarth could be considered. She is a skilled warrior, and in a femdom story, she could use her physical strength and her sense of honor to be in a dominant position, especially over those who disrespect her or the values she stands for.
Margaery Tyrell is a shrewd and charming character. A male OC who is involved in the political games of Westeros in a different way could intrigue her. Brienne of Tarth, despite her tough exterior, has a heart of gold. A male OC who sees past her appearance and values her loyalty and courage could make her part of the harem. And then there's Missandei, who is intelligent and well - spoken. A male OC with similar intellectual pursuits could find a connection with her.
The Mother. In the existing lore, she is a major figure. In fanfiction, she could be more actively involved in the events of Westeros. She could be a guiding force, using her powers to heal the sick and wounded, and trying to prevent the bloodshed that is so common in the Game of Thrones world.
The Hound could be a Futa character. His already rough and tough exterior would be combined with a different physicality. His journey of redemption or his loyalty to certain characters could be explored in a new light, and his interactions with other fighters in the story would be more complex.
Tyrion Lannister could be involved. He's a clever character who might offer his unique perspective on Daenerys' weight gain. He could use his wits to help her navigate the political fallout if there is any. Jorah Mormont is another one. He's deeply loyal to Daenerys, and his reaction to her weight gain could be interesting. He might be protective or concerned in a different way than others. Varys too. He's always scheming and would see how he could use this new development to his advantage in the power games.
Maybe an outcast noble. They've been shunned by their family for their interest in the dark arts. So, they embrace necromancy fully and aim to use it to take revenge on those who wronged them. They start by raising the dead of their family's enemies, and gradually build an army of the undead. Their journey would be filled with self - discovery and moral quandaries as they delve deeper into the world of necromancy.
Daenerys Targaryen could also be a main character in an emperor - like role. She already had a strong claim to the Iron Throne and was a powerful leader. In a fanfiction, she could fully embrace her role as an all - powerful emperor, perhaps even uniting the Seven Kingdoms under her rule in a more forceful way than in the original series.
Well, there would obviously be the bastards themselves. They could be given names like Joffrey Jr. (even if it's just a fan - given name), a son who has all of Cersei's cunning and a thirst for power. Then there could be a daughter named Myrcella - like, after the real Myrcella but with a different personality. She might be more fierce and independent, not willing to be a pawn in the political games like the original Myrcella.
The children of the main characters could be the new protagonists. For instance, Jon Snow's possible offspring, if he had any, could inherit his noble qualities and face new challenges in a post - Game of Thrones world.
Well, revenge can be a theme too. Suppose a female character has been wronged in the male - dominated world of Westeros. In a femdom story, she could use her new - found dominance to get revenge on those who wronged her. And then there's the theme of leadership. Femdom can show how a female leader might lead differently from a male one. She could use her femininity as a tool of leadership while still being in a dominant position, much like Daenerys uses her charm and her dragons to lead her people.
Some of the more independent lords or ladies in Westeros could be allies. For instance, Lady Brienne of Tarth. She is a paragon of honor and if the bastard displays honorable intentions, she could offer her sword and protection. Also, the wildlings might see the bastard as a way to gain some influence in the south. If the bastard offers them something in return, like a place to settle or resources, they could form an alliance.