Ron would be furious. His best friend being 'stolen' by his former rival would make him feel a mix of anger, betrayal, and jealousy. Harry would probably be in a difficult position. He's friends with both Ron and Hermione, so he might try to mediate at first, but if Draco is being difficult, he'd side with Ron. Ginny would be protective of her brother and would likely be very critical of Hermione for choosing Draco. The Slytherins, on the other hand, might be initially shocked but then accept it as Draco asserting his power and getting something he wants.
The reactions of the other characters in this fanfiction scenario would be diverse. The Hufflepuffs might be a bit more understanding and hope that love can prevail over house differences. They would encourage Hermione to follow her heart while also trying to keep the peace. The Ravenclaws would be more interested in the intellectual aspect of it. They might wonder if Hermione and Draco have some sort of intellectual connection that she didn't have with Ron. Some of the minor characters like Luna Lovegood would have her own unique view. She might see it as a beautiful, if strange, union and believe that there are forces at work that we don't understand. Overall, the fanfiction could explore all these different reactions in great detail.
Harry could be initially shocked but then very happy for them. He might see it as a sign of hope in the midst of all the darkness. Ginny, on the other hand, could be a bit jealous at first, but then come to accept it and even give Hermione some relationship advice.
Harry would probably be furious. He's always been protective of Hermione, and he'd see Draco's actions as completely unacceptable. Ron might be a bit more vocal about it, perhaps even getting into a fight with Draco. Ginny, on the other hand, would likely comfort Hermione and be very supportive. Neville could be shocked and disappointed in Draco, as he's a character who values loyalty.
If Draco steals Hermione from Ron in fanfiction, it might show a different side of Hermione. She might be attracted to Draco's intelligence in a different way than Ron's loyalty. This could lead to new magical adventures where Hermione uses her knowledge in a more Slytherin - like way, influenced by Draco. It could also make for some interesting interactions between the Gryffindors and Slytherins, as now there's a connection between them through Hermione. The story could explore how love can cross house boundaries in a more extreme way than what we see in the original books.
Harry would be really shocked. He's used to seeing Hermione as his friend and fellow Gryffindor. If she was suddenly Draco's sister, he'd be very suspicious at first. He might think it was some kind of Slytherin plot. Ron would be even more flabbergasted. He has his own issues with Draco and to think that Hermione was related to him would be hard for Ron to accept. He might even be a bit jealous that Hermione now has this connection to a pure - blood family.
Hermione would likely be more analytical. She might start researching the legal aspects of the case, looking for loopholes or signs of a miscarriage of justice. She would be outraged if she thought Draco was being wrongly accused, as she values fairness and the rule of law in the wizarding world.
One possible motivation could be that Draco has changed. He might have seen the error of his ways and decided to do the right thing. Another motivation could be that he has feelings for Hermione, even if they are not fully realized yet. He doesn't want to see her in a bad situation, so he steps in.
One possible reason could be that Draco has had a change of heart. Maybe he realizes that Hermione is a person worthy of protection regardless of her House or her friendship with Ron. He might have seen some injustice about to befall her from Ron and his Gryffindor bravado getting out of hand.
Harry would likely be very protective of Hermione. He's her best friend, after all. He might confront Draco immediately and try to get Hermione to see that she doesn't deserve this. Ron would probably be angry too, and might even be more impulsive in his reaction, perhaps getting into a fight with Draco.
Well, Ron could get angry. He has a strong loyalty to Harry, and seeing Harry with Draco, who he has always seen as an enemy, might make him feel betrayed. He might immediately jump to conclusions and start shouting or demanding an explanation from Harry.
Yes, there are some out there. Some fanfictions explore this alternative relationship dynamic in interesting ways. They might rewrite the story's events and character interactions to make it seem more plausible for Harry to be with Hermione instead of Ron.