I think setting up a club QT tank is a separate and much more complex conversation.
It would have to consider responsibility/ liability, tank location, care for all animals in QT, openness/restriction of access to the system, contingencies for infections/deaths/contamination (wouldn’t you be pissed if someone else’s fish in your QT batch infected and killed your $300 fish). Also there would be limited use, as only 1 batch could be done at a time... as well as many other factors.
It’s a great idea, but certainly complex. It would be much easier to set up a private QT tank (amongst friends) and simply make it open for the club to use. The owner would accept all care requirements, and participants would get involved at their own risk. Details could be agreed on privately. But even so, that would be a different conversation than a group buy for purple tangs.