The plot could take a turn where Zabini is initially seen as the bad guy because of the kidnapping, but in reality, he is trying to protect Hermione from a greater threat. Maybe there's a prophecy that involves Hermione and Zabini, and the kidnappers are trying to stop the prophecy from coming true. Another possible twist is that Hermione's kidnapping leads to a discovery of a long - lost magic that Zabini's family has been searching for. This magic could change the balance of power in the wizarding world, and now Hermione is in the middle of it all.
One possible plot twist could be that the kidnappers were actually working for a powerful dark wizard who wanted to use Hermione's intelligence for his own evil plans. Maybe they planned to brainwash her into becoming a powerful weapon against the wizarding world. Another twist could be that Hermione's real family had a dark secret and the kidnapping was an attempt to keep her away from it. For example, her family might have been involved in some sort of ancient dark magic that they didn't want her to discover. Or perhaps the kidnappers thought they were rescuing her from a prophecy that would bring doom to her if she stayed with her birth family.
One idea could be that Draco and Zabini kidnap Hermione for some sort of political gain in the wizarding world. Maybe they think her knowledge or influence can be used to their advantage. For example, they could be part of a group that wants to change the power structure at Hogwarts and believe Hermione holds the key to making it happen.
One possible plot twist could be that Draco actually has noble intentions behind the kidnapping. Maybe he's trying to protect Hermione from a greater threat that she's unaware of. For example, there could be a dark wizard targeting her specifically, and Draco, despite his past enmity, decides to take matters into his own hands to keep her safe.
One possible plot could be that Dumbledore has been possessed by a dark entity. Under its influence, he kidnaps Hermione thinking she has some knowledge or power that the entity wants. Hermione then has to use her wits to try and break Dumbledore free from the possession while also trying to escape.
A really interesting plot twist might be that Voldemort is being controlled by an even darker force, and Harry has to figure out a way to break that control while being held captive. Or perhaps Harry's friends, thinking he is dead, accidentally start a chain of events that end up helping Harry escape in a very unexpected way. For example, Hermione might cast a spell that was supposed to be for protection but ends up creating a portal right in Voldemort's lair.
A really unexpected plot twist in this kind of fanfiction might be that the kidnapping was a mistake. The kidnapper was actually after someone else but got the wrong duck. This could lead to all sorts of comical or tense situations as they try to figure out what to do with the wrong captive. Also, the kidnapped character could discover a long - lost secret about their family during their captivity, which changes the whole dynamic of the story.
Perhaps Bellatrix kidnapped Hermione to use her as bait to lure Harry. Bellatrix has always been extremely loyal to Voldemort and might think that by having Hermione, she can draw Harry out into the open. Hermione, being the intelligent witch she is, could try to outwit Bellatrix while in captivity, maybe by finding a way to send messages to her friends or even by trying to escape on her own.
One possible plot twist could be that Jasper is being controlled by an external force, like a powerful vampire with mind - control abilities. So, he doesn't really mean to kidnap Bella in his true self.
In this fanfiction, Zabini could develop in several ways. At first, he may seem like a typical villain, but as he spends more time with Hermione, he realizes the error of his ways. He could have a backstory that is revealed, explaining why he got involved in the kidnapping in the first place. Maybe he was forced into it. As the story unfolds, he might grow to respect Hermione and even fall in love with her, which would completely transform his character from a kidnapper to a protector.
A big plot twist could be that Artemis was actually faking his kidnapping as part of a bigger plan to infiltrate an enemy group. He lets himself be taken so he can gather intel from the inside.