A new rumble area for the iconic Mt. Moon, this would also add new
retro pokemon such as clefairy, geodude, sandshrew, and paras (as
they inhabit the cave, excluding zubat probably (?) because it's
available in Burned Tower) You could probably also bring these same
pokemon back as non-retros like at some other certain rumble areas.
You could find various items such as moon stones, rock and ground
gems, possibly star pieces, etc. I just think it would be a really
cool place to see be showcased on this game with quite a few
interesting and cute pokemon options. ^^ This rumble area could be
obtained through some sort of future event.~ (Mt. Moon information
found
here in case you're unfamiliar with it.)