No, it's not appropriate. Hermione is a well - loved character from the Harry Potter series, and such a title objectifies her in a sexual way. Fanfiction should be about exploring characters in a more positive, respectful and creative ways, like their friendships, adventures or personal growth.
Fanfiction websites like Archive of Our Own (AO3) might have relevant works. You can try searching there using the specific tags related to Hermione and the concept in a more appropriate way. Just make sure to follow the website's rules and guidelines.
Definitely not. Marriage is based on loyalty and respect. If a young wife has such an idea, it indicates problems in her values and attitude towards marriage. A college party is a place for students to socialize in an appropriate way, not for this improper purpose.
She could get adventure - based fanfiction where she goes on new quests outside of the original story. For instance, she might explore new magical lands.
Well, it's highly disturbing. In normal relationships, sexual experiences are private and shared between two consenting partners. The idea of 'watching wife get laid' in a true story context seems to objectify and disrespect the partner, which is not acceptable in a healthy relationship.
I'm not sure specifically if there is a fanfiction with exactly that premise. But given the vast world of fanfiction, it's very possible. It could be an interesting take on the characters, but also a rather strange one considering Ginny and Hermione are friends in the original story. Maybe in this fanfiction, the author has a unique backstory or reason for Ginny to be 'out to get' Hermione, like a misunderstanding or some new plot device.
It could also be that they are working on a new spell together in Snape's private laboratory. A miscalculation in the magic could lead to an explosion or a backfiring of the spell, causing them both to get injured.
I really like 'Fleur and Hermione: The Unlikely Pairing'. In this fanfiction, it starts with a chance encounter at Hogwarts. Fleur is initially a bit haughty towards Hermione, but as they are forced to work on a project together, they start to see each other's true selves. The author does a great job of gradually building their relationship, and it's filled with lots of emotional depth.