Don't paw at me with your dirty little guild.
I don't wanna join your goddamned union, all right?
Loner. Lone gunman. Get it? That's the whole point.
I like the lifestyle, the image. Look at the way I dress.
Look, this is a one-on-one business. The minute you start relationships, bad things start happening
Oops! Sorry about that. Those are quotes from the movie
Grosse Pointe Blank that rang through my head when I read the title of this thread. I've obviously watched it too many times.
For this to work I think the association (instead of "guild", to stop Martin Blank chattering away in my head) would need to support a "guest" membership open to most writers. Without that I think potential participants may never get to see any advantage for them, especially early on. Full membership (with rights to advertise as part of the guild etc.) would go through the sort of vetting procedure you've suggested.
There are so many author associations and writers' groups already that I think it would be difficult to "sell" the advantages of another. On the other side of the argument: many writers do seem to be "joiners", if the number of existing groups is anything to go by. Since I'm not really a joiner (my report card says I don't play well with others) so I don't have first hand experience of what happens in such groups (MobileRead is something of an exception for me).
You have already noted the potential need for separate reviewers for litfic, I suspect you may find need for even more divisions - although I suppose that could grow over time as the need revealed itself.
The association would have to be very strict in its standards. Such an association would only be useful and effective if it gained a reputation for only allowing high quality work through. Such a strict regime is certain to generate a lot of internal heat, and that will make it difficult to hold it together. The key, I believe, would be to make sure that strict standards are clearly stated and relate to the quality of the work presented rather than story content or style. The association must be a gatekeeper, but not in the sense of what sells, but in the sense that any work approved through the association must meet high language standards and specific technical requirements (formatting and so on).
But despite those reservations, I do like the idea. If it could be made to work it might be a way for quality work to find distinction from the slush pile that has so many disregarding self-published works out-of-hand.