I've seen people do something like that before unofficially where to join a game run by them, you had to be an approved member. I don't think it ever took off.

Honestly, the concept is kind of divisive and you're dealing with something that can cause a lot of petty conflicts and newer members feeling ostracised. Imagine being new to the guild and seeing that most RPs are exclusive clubs that you can't join unless you apply, and while you may counter with "but they can just apply to those guilds!", consider that a big reason a lot of people don't play in advanced is because they see it as an elitist club, or think they aren't good enough when they write excellently.

Fractured communities is not a great idea.