Another common plot twist is Hermione having a hidden connection to one of the other schools participating in the tournament. Maybe she discovers that she has family ties to a student from Beauxbatons or Durmstrang. This connection then leads to her getting involved in political or magical intrigue between the schools that wasn't present in the original story. It can involve her using her intelligence to navigate through these complex relationships and keep Hogwarts safe.
One interesting plot twist could be that Hermione is secretly entered into the Triwizard Tournament not by the Goblet, but by a dark wizard who wants to use her as a pawn. This would put her in a very dangerous situation right from the start.
One interesting plot twist could be that Hermione discovers a hidden spell within the Goblet of Fire that no one else knew about. This spell could change the nature of the Triwizard Tournament in unexpected ways.
One interesting plot twist could be that Harry has an unexpected ally in the Triwizard Tournament. Maybe a Slytherin student who has a hidden agenda but ends up helping Harry in a crucial task. This would change the dynamic of the traditional House rivalries.
Maybe Harry travels back in time and discovers that the person who put his name in the Goblet was actually an older version of himself trying to change the past for some reason. It could be that in the future, something really bad happened and he thought by changing this event in the past, he could prevent it. This would create a really complex and mind - boggling time - travel paradox.
One interesting plot twist could be that Hermione's snake form is actually a key to unlocking an ancient prophecy. In the fanfiction, no one realizes this until she accidentally discovers it while in her snake form exploring an old chamber. This could change the whole course of the story as everyone now has to protect Hermione and figure out how to fulfill the prophecy.
Well, it could be that Hermione accidentally drinks a love potion during the Goblet of Fire events. Harry is the only one who can break the spell. The 'lemon' aspect might be some flirty and slightly spicy interactions as Harry tries to bring Hermione back to normal. For example, a scene where Harry has to hold Hermione's hand a bit longer than necessary while reciting a counter - spell.
One interesting plot twist could be that instead of Cedric Diggory being the Hogwarts champion, Neville Longbottom is chosen by the Goblet of Fire. This would completely change Neville's character arc in this part of the story, as he'd have to face much more danger and scrutiny. It could also lead to new friendships and rivalries.
One interesting plot twist could be a character who was thought to be a friend actually being in league with the Death Eaters all along. For example, a minor character like Seamus Finnigan could be secretly working for Voldemort, passing information about Harry's movements. This would add a whole new layer of danger and suspicion to the story.
One interesting plot twist could be that Fem Harry forms an unexpected alliance with a Slytherin student. Maybe she realizes that not all Slytherins are as bad as they seem in the context of the Triwizard Tournament. This changes the whole dynamic of the story as she now has an inside source in a house that was previously seen as her rival.
One interesting plot twist could be Draco secretly helping Harry Potter in the Triwizard Tournament tasks. Maybe he realizes that there's a greater danger at play that could affect both the wizarding world and his own family, so he decides to put aside their rivalry for a while.