It is not ethical. Hinata Hyuuga is a character, and creating fanfiction that involves abuse goes against the spirit of respecting the character and can also be disturbing to other fans who love the character for her positive traits.
Love and relationship are very common. Since they are a popular couple in the Naruto series, many fanfictions explore how their relationship develops further, like their married life or how they deal with challenges as a couple.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. They have a large collection of fanfictions on various topics, including those about Naruto and Hinata.
They would probably be very proud. Despite their differences, both Hinata and Neji are highly skilled members of the Hyuuga clan. For the clan, watching them fight in the fanfiction would be like seeing the best of their combat techniques and kekkei genkai on display. They might also be analyzing their moves to see how they can further improve the clan's fighting style.
Well, the Hyuuga clan has certain expectations and standards. Their presence during the Hinata vs Neji fight in the fanfiction would make both fighters more conscious of these. Hinata, who has always been in Neji's shadow in the eyes of some in the clan, would be trying extra hard to show that she can be a great Hyuuga. Neji, who has always been seen as a strong representative of the clan's old ways, would be fighting not just to win against Hinata but also to maintain his status among the clan. Their fight is thus shaped by the clan's overarching influence.
In a Naruto pranks Hyuuga fanfiction, Naruto might use his typical mischievous tactics. For example, he could use his shadow clone jutsu to create chaos around the Hyuuga compound. Maybe he'd make clones that pretend to be important visitors and then act all silly to embarrass the Hyuuga. It would be a really funny scenario as the serious Hyuuga clan tries to deal with Naruto's antics.
One aspect to consider in Natsume Hyuuga x OC fanfiction is the character development. The OC can bring new dynamics to Natsume's character. For example, if the OC is a very outgoing and adventurous person, it can contrast with Natsume's more reserved nature and lead to interesting interactions. It also allows for exploring different storylines that may not be possible within the original canon. Writers often use this type of fanfiction to delve deeper into Natsume's emotions and relationships in a more personalized way.
I recommend 'Mikan and Natsume's Promise'. It's a short but heart - warming fanfiction. It focuses on a promise they make to each other and how they uphold it throughout different situations.
Family loyalty is also a big theme. Since the Hyuuga clan has a complex family structure, many fanfics revolve around the relationships between family members, like siblings or parents and children, and how they support or conflict with each other.