This is a really interesting and dark fanfiction concept. In the Harry Potter universe, Draco and Ginny are from different houses and have different loyalties. If Draco were to kidnap Ginny to marry her, it would go against her will and the values of the wizarding world. However, it could make for a very intense and dramatic story, exploring themes of power, love, and coercion.
One possibility is that it could be a dark and twisted take on the relationship between Draco and Hermione. Maybe in this fanfiction, Draco has some ulterior motives that lead him to this extreme act. It could explore themes of power and control as he forces Hermione into a situation she doesn't want. However, it also might lead to a redemption arc for Draco as Hermione tries to change his ways.
She would most likely be furious. Hermione is a smart and independent character. She would immediately start planning her escape. She might use her knowledge of magic to try and outwit Draco.
In many fanfictions, Draco and Ginny having a daughter often creates an interesting dynamic. Their daughter might inherit traits from both of them. For example, she could have Draco's cunning combined with Ginny's fiery spirit. This can lead to unique storylines where she has to navigate the complex wizarding world, facing challenges that come from the history of her parents' houses, Slytherin and Gryffindor.
Often, it ends with Draco having a change of heart. He realizes the wrongness of his actions and releases Ginny. This could be due to seeing Ginny's vulnerability or her kindness towards him even in captivity. They might even become friends or something more in some cases. Another common ending is that Harry and his friends rescue Ginny. There's a big showdown where they outwit Draco and his accomplices and save Ginny.
One possible plot could be that Harry plans a very elaborate and private proposal. He takes Ginny to their favorite place in Hogwarts, perhaps the Room of Requirement set up as a beautiful garden filled with the flowers Ginny loves. He gets down on one knee and tells her how she has been his rock through all the post - war chaos and how he can't imagine a future without her.
One way it could end is with Ginny escaping on her own. She could use her quick thinking and magic skills to break free from Draco and make her way back to her family. This would show her strength and independence.
A Draco - Ginny pregnancy fanfiction could involve a lot of drama. For example, Ginny might struggle with how the wizarding community would view her being pregnant with Draco's child. And Draco might have to face his own prejudices and those of his family. There could be a lot of tension and character development as they navigate this new situation together.
One consequence could be a huge rift among their friends. Harry's friends would surely be against this forced union and might try to rescue him. For Draco, his friends might also be divided as some may not support such a cruel act.
In some fanfiction, this could happen due to a power play. Maybe Draco's family still has some influence and he uses it to force Harry. It could also be a result of a misunderstanding or a dark plot twist where Draco believes he has no other choice to get what he wants.
Maybe Draco is jealous of Hermione's intelligence and abilities. In the fanfiction world, he could think that by making her his wife, he can somehow take credit for her achievements or keep her from outshining him. It could also be a power play. Draco might believe that having Hermione under his control through marriage would give him more influence in the wizarding world, especially if she has connections that he wants to use for his own gain.