So, I've had these two stories knocking around in my head for a while and since they aren't doing me any good I figured they might be able to inspire someone else.
The first comes from a fic I read many years ago and for the life of me, I can't seem to find it again. It took place during the Deathly Hallows when Hermione used the polyjuice potion to turn into Bellatrix. After she took it she had the urge to kill Harry and that's about as far as it went. It was super short but this story stuck with me. My idea was that she would be afraid that the goblins of Gringotts might realize she wasn't Bella, so she might use an older more powerful version of the potion that she may have come across during her time a school. The potion would have the side effect of having the persons mind slowly change the longer they stay transformed. It wouldn't get too far because the waterfall washes it away but after the battle at Hogwarts she starts to have dreamed where she is Bella and realizes she liked the way it felt to be her. So Hermione in secret starts to use the potion again going so far as to go outside as Bella, sparking rumors of people seeing the ghost of Bellatrix or that she might have survived the battle. She becomes addicted to being Bellatrix and begins spending more time transformed than her self. Each time she changes back she mentally takes on more of Bellatrix traits and personality until she decides to try to find a way to stay changed for good. She would then become the next would be dark lord.
The second one involves Hermione finding out more about her magical heritage. It would start with another snide remark from Draco which inspires her to start looking into her family. She would get the family tree from her mother and fathers sides of the family and would notice that the two "> had been charmed. When she brings the two together, they would combine, revealing that her mother and father "> come from the same magical family. It would be some old magical pureblood family that had been thought to have died out, but one member had denounced the magical world and lived as a muggle. His last magical act would be to cast a spell on his children to hide them from the magical world and erase the memories of their siblings so their blood would never mix and the bloodline would become deluded and die out. Then Hermione's parents would meet and have her, and when she started to go through puberty the two magical parts of blood would ignite. It would spread like a virus in her blood, destroying the muggle part and leaving only the magical part. I also figured Draco would find out and blackmail her because she doesn't want anyone to know, I always pictured this as a Dramiome story. This is my take on the pureblood Hermione trope.