A really engaging storyline could be that their children are somehow transported back in time to the era of the Marauders. There, they have to figure out how to get back to their own time while also not changing the past too much. Along the way, they might learn more about their parents' and their parents' friends' pasts, and form unexpected friendships with the young versions of people they know.
One interesting storyline could be their children starting at Hogwarts and facing new, unforeseen magical challenges that Harry and Hermione have to guide them through. Maybe a new dark wizard is on the rise and their kids are the ones who first notice the signs.
Another could be that their children inherit some unique magical abilities that neither Harry nor Hermione have. For example, one of their kids might be able to communicate with magical creatures in a way that no one else can. This could lead to all sorts of adventures where they discover new species or solve mysteries related to existing ones. In the fanfiction world, the possibilities are really endless.
One interesting storyline could be a magical adventure where the three of them team up to solve a mystery in the wizarding world. For example, they might be on a quest to find a lost magical artifact that has the power to save Hogwarts from a new dark threat. Hermione's intelligence, Fleur's charm, and Harry's courage would all play crucial roles in this adventure.
One interesting storyline could be Hermione and Pansy having to work together on a school project. At first, they clash because of their different personalities and house loyalties. But as they dig deeper into the project, they start to understand each other more. For example, they might be researching a dark wizard from the past and realize that they both have a thirst for knowledge and a desire to do good in the wizarding world, despite their initial animosity.
Perhaps a storyline where Hermione is a mother in a post - war wizarding world. She has to raise her children in a society that is still rebuilding, teaching them values of peace and unity. This could involve her sharing her own experiences from the war to instill important life lessons.
One interesting storyline could be Hermione finding herself in Gotham City and having to use her magical skills to outwit the Joker. Maybe she tries to stop his evil plans without revealing her magic to the non - magical inhabitants of Gotham. Another could be the Joker getting his hands on some magical item from Hermione's world and she has to retrieve it. For example, if he got a powerful wand, Hermione would need to use her intelligence and magic to get it back before he causes chaos with it.
One interesting storyline could be where Deadpool somehow gets transported to the wizarding world. He'd be his usual chaotic self, confusing the hell out of everyone, especially Hermione. She might initially be put off by his insanity but gradually see his good side as he helps in some sort of magical - mutant mash - up adventure, like fighting a new dark wizard - mutant hybrid villain.
Another storyline might involve Ginny and Hermione teaming up to solve a mystery within Hogwarts. Maybe there are strange disappearances of students and they use their combined skills, Ginny's Quidditch - related quick thinking and Hermione's vast knowledge, to get to the bottom of it. They might suspect a hidden chamber or a rogue spellcaster. They start by interviewing students and staff, gathering clues from different parts of the castle, and finally unmask the culprit.
One possible storyline could be that in a hidden corner of Hogwarts, Snape discovers Hermione's secret project related to advanced potions. This could lead to a begrudging respect as he sees her intelligence and determination, similar to how he respected Lily. Another could be Hermione stumbling upon Snape in a corner where he is reminiscing about his past, and she gains a new understanding of his character.
One interesting storyline could be Hermione getting involved with the Black family secrets. Maybe she discovers a hidden Black family magic that could change the wizarding world. For example, she might find a spell that has been lost for centuries within the Black family library.
Another storyline might involve a time - travel scenario where Hermione goes back in time and encounters a younger Fenrir Greyback. She attempts to change his path, to prevent him from becoming the cruel werewolf he is known to be in the future. This could involve her using her knowledge and magic to offer him a different future, but facing many challenges along the way.
A great storyline could be the daughter having a unique magical ability that neither of her parents have. This could lead to her being both feared and admired at Hogwarts. In some fanfictions, she uses this ability to solve mysteries around the school. There could also be a story where she has to choose between following the Slytherin or Gryffindor values more closely, as she has a connection to both through her parents. This internal struggle can make for a very engaging read. And of course, a plot where she gets involved in a time - travel adventure related to her parents' Hogwarts years would be really exciting.