yes you could keep quail in there. In my experience they won’t use the coop part in the same way as chickens do, (i attempted to put all 7 of mine in a coop every night for the first few weeks outside) but some of mine do climb the ramp in my 2 level grow out hutch. mine have done well outside through the winter here but I did bring the adults in during the “arctic blast” and kept a coop heater in the grow out hutch for a couple of weeks. as far as # of quail in that space....best answered by kiki or 007 etc. all my birds have done well but i’ve heard some horrible stories of aggression by both male and female quail.
#22 did kind of sort of started to hatch but never quite got all systems online. 
