No, it's not appropriate. Writing 'dirty' fanfic, especially with inappropriate sexual content, violates ethical and moral standards. Fanfic should focus on positive, creative interpretations of a character or person rather than delving into inappropriate and disrespectful areas.
The main ethical issue is the disrespect to Bryce Hall as a person. He has his own identity and rights, and this type of fanfic objectifies him in an inappropriate way.
In a Bryce Hall and Blake Gray fanfic, the possibilities are endless. It might focus on their friendship and how they support each other through the ups and downs of their careers. For example, they could be working on a big project together and face challenges that they have to overcome as a team. Fanfics are a great way to expand on the personas we see in real life.
Another aspect of a Bryce Hall and Blake Gray fanfic could be their personal growth. For instance, they could both be going through a difficult time in their lives and help each other to become better versions of themselves. The fanfic could explore their emotions, their insecurities, and how they support one another through it all. It's a great way for fans to delve deeper into the personalities of these two individuals.
One idea could be Bryce Hall getting involved in a mystery adventure in his hometown. Maybe he stumbles upon an old abandoned building and discovers a hidden secret about the town's past.
First, do some research on Bryce Hall. Know his personality traits, his hobbies, and his public image. Then, think of an interesting scenario or a problem that he could be in. For example, you could start with him having a misunderstanding with a friend.
Sadly, there's no public knowledge about whether Bryce Hall has an affinity for reading fanfiction. Fanfiction can be a very personal form of entertainment. Some people love it for the freedom it gives to expand on existing fictional universes, while others might not be interested. Without Bryce Hall saying anything about it, we can only wonder if he's part of the fanfiction - reading community or not.
As I don't know the specific 'girl on Bryce Hall story', I can't say who the girl is. It could be a girl from his personal life, like a friend, a romantic interest, or someone he worked with on a project. Without more details, it's impossible to identify her.