Great list!

I would only add one subdivision, perhaps 3b: highly seasoned players who are willing to do requests. Maybe they play (or
played) the song in one of their other bands, or maybe they've simply heard it enough that they can just fake it.
It doesn't mean anything goes, but I've been amazed by the requests some local "super groups" have pulled off: the BL will ask his mates "what about X?"; if everyone concurs then they go for it, and the best play it like they've rehearsed it. The super groups are made up of the guys you can call in to sub on minimal notice (if they're available), and still be certain they'll nail your gig.