One possible plot could be Nagini's struggle between her loyalty to Tom Riddle and her own humanity. Maybe she starts to question Riddle's dark deeds as she still has human emotions. For example, she might try to prevent him from harming an innocent person.
Nagini's human form could potentially disrupt Tom Riddle's plans. Since she has human emotions in this form, she might not be as blindly obedient as she is in her snake form. For instance, she could show mercy when Riddle wants her to attack someone, which would be a hindrance to his dark plans.
Another plot could involve a time - travel aspect. Ginny Lemon could somehow be sent back in time to when Tom Riddle was a student at Hogwarts. She might try to change his path towards the dark side by showing him kindness and understanding, but things could go awry as Tom's ambition and insecurities still drive him towards the dark arts, and Ginny has to deal with the consequences of her actions.
One interesting plot could be a time - traveling character going back to Tom Riddle's school days at Hogwarts. They could try to prevent him from becoming Voldemort by befriending him and showing him a different path. For example, introducing him to the power of love and friendship which he lacked in his original life.
Well, a plot could be that Ginny has some sort of premonition about Tom Riddle's future as Voldemort. She then tries to change his path in the lemon fanfiction. This would create a lot of tension and emotional turmoil as she battles with her feelings for him and the knowledge of what he could become. Also, there might be a plot where Tom Riddle is actually conflicted about his feelings for Ginny and his dark ambitions, which makes for a very angsty and engaging story.
One interesting plot could be a time - travel scenario. Hermione somehow travels back in time to Tom Riddle's Hogwarts days. She tries to prevent him from becoming Voldemort. Maybe she uses her knowledge of magic and the future to show him a different path, like introducing him to the power of love and friendship that he was deprived of as a child.
Well, a possible plot is that Hermione discovers a hidden diary of Tom Riddle that has some sort of magic she has never seen before. As she delves into it, she somehow gets connected to Tom's memories and experiences his past. This could lead to her trying to understand what made him turn out the way he did and she might attempt to change his future. Another plot could be that in an alternate universe, Tom Riddle didn't become evil and he and Hermione meet at Hogwarts as normal students. They end up competing in academics and gradually develop a strange sort of friendship that challenges both of their beliefs.
In some fanfictions, there could be a time - loop situation. Harry and Tom Riddle keep repeating a certain period of time, and each time they interact, they learn something new about each other. For example, they might start off as enemies but gradually come to understand the reasons behind each other's actions as they repeat the time period over and over again.
Well, there could be a plot where Hermione, through a spell gone wrong, enters a dimension where Tom Riddle won the wizarding war and rules with an iron fist. She has to pretend to be on his side to survive and in the process, she discovers some redeeming qualities in him that she didn't expect. Another idea is that Hermione is researching a new form of magic that was only experimented with by Tom Riddle. As she tries to replicate his experiments, she accidentally summons a part of his spirit and they engage in a battle of wits and magic. And yet another plot could be that Hermione is sent on a mission to stop a new dark wizard who is using Tom Riddle's old methods, and in order to understand the enemy better, she uses a time - turner to go back and study Tom Riddle directly, which leads to unexpected interactions and consequences.
One possible plot could be Hermione using her modern knowledge and magic skills to raise Tom in a more positive environment. Maybe she teaches him about equality and kindness from a young age, which changes his view of the wizarding world and prevents him from turning into the dark lord. For example, she could introduce him to muggle culture and values, making him more accepting of different kinds of people.
One interesting plot could be a time - traveling character going back to Tom Riddle's school days at Hogwarts. They might try to prevent him from becoming Voldemort. For example, they could befriend young Tom and show him a different path of magic, one that's more about using it for good and building relationships. This could change the entire future of the wizarding world.