I like the idea of having both ranked and unranked pugs, here are some thoughts:
My perception of ranked pugs would be the standard captain draft, though I'm unsure about separating by division. It may be better to start small and see where things go from there. (throw in some ELO ratings; commends would also be sick IMO). Unranked pugs would be more akin to mixchamp (I don't remember how it functioned exactly, but I'm pretty sure it just randomly placed six players on a team once the min class reqs were met).
As biased as I am towards casual/goofy pugs, I think it's important for everyone to be open to this discussion, doubly so if we intend to use RGL pugs as a foundation. For now, I'm glad this thread has been made.
If possible, could we go on a quick tangent and discuss why we don't use RGL Pugs? These came about while I was away from the game, and I have never seen a single player added up to them. Surely discussing why we don't use the site will kickstart its improvement?
IIRC, someone mentioned HL and 6s share servers that are in short supply. In this case, why not let us provide our own servers à la tf2c? I'll admit I'm not sure what that would look like or if it would work at all, but I'm just throwing around whatever first comes to mind.