Luna Lovegood could be an interesting choice. She has a very unique view of the wizarding world. As a DADA teacher, she would teach in her own offbeat way. For example, she might introduce the students to the idea of defending against invisible creatures that most wizards don't believe in. Her lessons would be full of creativity and would make the students think outside the box.
Sirius Black, if he hadn't died. He had a lot of knowledge about dark wizards and magic, having grown up in a family with a strong connection to the dark side. He could pass on his knowledge of how to recognize and counter the dark arts, and also share his own experiences of escaping from dark influences. His teaching would be full of passion and a bit of rebellion.
Remus Lupin was already a great DADA teacher. But in a new fanfiction, he could return in a different form, like being brought back by some new magic. He could continue his teaching with even more wisdom and experience, especially teaching the students about the importance of acceptance, as he himself was a werewolf and had faced discrimination.
One great fanfiction could be where the new Dada teacher is secretly a time - traveling wizard from a future Hogwarts. He uses his knowledge of future dark magic threats to prepare the students in a really unique way.
Maybe the new Dada teacher was once a student who was deeply affected by a dark magic encounter. So, he came back to teach DADA to make sure no other students have to go through what he did.
One possible plot could be that the new DADA teacher has a mysterious past related to an ancient dark magic artifact. He or she initially seems friendly but gradually the students start to notice strange behavior. For example, they might find the teacher secretly researching in the Forbidden Forest at night. This could lead to the students, especially Harry and his friends, trying to uncover the truth about the teacher and in the process, they discover a plot to bring back an old dark wizard.
A great fanfic idea could be that the DADA teacher is actually an animagus who uses their animal form to secretly spy on the Death Eaters. They could be a cat or a bird, for example. In the fanfic, Harry and his friends might start to suspect something strange about the teacher when they notice the animal always seems to be around when important information is being passed. Eventually, they discover the truth and the teacher becomes an even more important ally in their fight against the dark forces.
Another challenge for Harry as Dada teacher could be dealing with the school's bureaucracy. He might want to introduce new teaching methods or change the curriculum, but he has to go through the proper channels. And there could be resistance from some of the more conservative teachers or the school administration who are used to the old ways of teaching Dada.
Well, in this fanfiction, Harry might use his own experiences with dark magic to teach in a very practical way. For example, he could share how he faced Voldemort and his Death Eaters and turn those real - life situations into lessons on defensive magic. He might also introduce some new spells that he has learned or developed during his adventures.
An old ex - Auror who now lives near Hogwarts. He could have a past connection to Voldemort and some knowledge about the Dark Arts used in the Triwizard Tournament. He becomes an unofficial mentor to Harry, teaching him some unique spells and strategies that are not part of the regular Hogwarts curriculum. This character could bring a new perspective and a bit of wisdom to the story.
A really cool fanfiction idea is one where the DADA teacher was once a student at Hogwarts who failed the subject miserably. Now they've come back as a teacher to prove that they've mastered the subject. Along the way, they face challenges like old bullies who are now colleagues and students who doubt their abilities.
Time travel can give the DADA teacher a chance to change things. They could try to prevent certain dark events from happening in the past. But this also comes with risks. If they change too much, they might disrupt the entire timeline. In some fanfics, the teacher has to be really careful about what they do and say to not cause chaos in the wizarding world's history.
One great fanfiction in this genre is 'The Time - Twisted DADA Teacher'. It has an interesting plot where the DADA teacher from a future time travels back to Hogwarts during Harry's time. The character development is well - done and it weaves in elements from the original series in a creative way.