Wow, this is really dense as usual!
I think my first comment would probably be to simplify it. Something that I think I've started to develop a better sense for is that complicated quests aren't popular and they simply don't get taken except by the same 1-2 players. I think this is similarly true for regions. If it's a struggle to summarize the region in ~100 words, then it's probably too complex for most players to find it really approachable.
The second is that there's too much content packed, and at least split it into multiple regions (I think I said similar things about your original Spire Reef too?). Underground Kingdom is clearly it's own region, as is the Mecha Kingdom. Merging them just gets messy.
My third comment is that "exploration quests" don't fill a whole quest board (~50 quests per region). It's literally
one quest: "Explore the Dungeon" -- and then the quest board ends up being blank(???). It's too open-ended to really provide a solid sense of guidance, and ends up being equally open-ended as a shape-shifting dungeon quest that at best can only provide a tiny handful exploration quests? This is in contrast to an ordinary dungeon where you can have an: "Explore the Fifth Floor East Dungeon - Arctic Biome" where it's more tightly constrained.
My fourth comment was something that Alice was worried about in previous versions of AG, but there's a serious concern that characters who start spawning tons of high-value artifacts for cheap especially since it is so easily attainable on a Guild Quest. There ends up being severe power creep due to infinite artifact inflation, and power creep is something that I intend to regulate extremely tightly on this version of AG.
And I think those are my main comments for now! ^^