Also, the nature of such guilds thematically makes it a bit weird to advertise. Carlsan can't exactly say "Oh, and if you wanna be a thief, go join the thief school. You can find it e;e;n; from the basket in Kabal. Take the ship from pier 11".

The only thing I could think of would perhaps be some sort of hunter/ranger type of guild, still stealthy, can dodge damage (like you said), can sneak up on enemies to start a fight or something, but not focused on stealing from or murdering other players.
But even if we find a good theme and skillset for it, I am still not convinced. I think newbies are better off meeting other people, talking to other people, etc. Sneaking around without being seen, and likely be distrusted by older players (especially if we include pick picket skill) is maybe not the best way to learn Genesis?
For this kind of guild I think it's perfectly fine, actually preferable, if you discover it a bit later in the game, when you know a bit more, and know a bit more about who you character is going to be.