There is something similar in Indiana. I know of several people that use it regularly to trade guns.
Remember that event in Pinetop-Lakeside, of a “no dealer” gun show? Chaos was avoided because it was snowed out, fortunate because the venue was just a fraction of the size it needed to be able to handle the projected crowd.
Yet this shows the enormous potential of such events.
In truth, a smaller gun exchange might be a much better idea, precisely because it avoids such a crush.