One interesting plotline could be a different take on the Triwizard Tournament tasks. Maybe the challenges are not as straightforward as in the original, with hidden twists and alliances among the champions that we don't see in the book. For example, the champions might have to work together in some tasks secretly to overcome a greater threat that the judges don't know about.
Another plotline could involve a different set of characters getting chosen as champions. Instead of the usual suspects, it could be some lesser - known students from different houses who have unique skills and backstories. This would completely change the dynamics of the tournament and how the story unfolds, as they would approach the tasks with different strategies.