I like "The Scholars" and "The Archivists" but it lacks something, an edge?
I think it would fit to have a group of 4 with a name that says more of what they do than where their lair is?
A combination of what they do and where they are perhaps?
Also, their missions won´t just be one hit assassinations, as I understood (although not familiar with Blades in the Dark) it´s everything criminal, heists, smuggling, kidnapping etc?
"Literal Cartel" would speak more of both where and who they are imho.
When speaking to a new client or on a mission they could speak to eachother by the first letter in their names- like codenames Reservoir Dogs style- that could be a signum when they were fighting an enemy they would know if they heard the crew talking to eachother.
-Hey guys did you hear? "B" from "Letters"-(known in the underworld) took down a hole building in China Town? Apparently he used brute force to knock down a supporting wall"
I dunno.. that´s the best I can make up...