I wonder if they could do something like turn A ranks into quests you can grab at the Hunter Scholar and once you get the quest you need to go activate the conditions for spawning them based on clues from the Hunter Scholar, once your party manages to spawn it then you get a open world zone cordoned off the the population like Bozja uses in their zones. This zone would be for an 8 player party only, as SE intended, and giant player mobs would be a thing of the past plus the original intent of 8 players spawning and fighting A ranks would be preserved, plus the work for it would be rewarded to the party only. No freeloaders.

Since any party can grab the quest they could simply be RNG into different areas of the world so as to handle lots of parties doing this simultaneously.