For XIV, adding a closed-off map area that's only enterable by having the invite to trade to a gatekeep on a highly-desired map would be pretty simple. Have it retain some of the sights from the map, such as, say, a forested waterfall in the Shroud, a desert oasis in Thanalan, a tropical island for Limsa, or on the moon with the world in the bg. They don't really have a way to do layered instances, seeing as how they don't have them beyond the numbered system we have now (for, say, "Mor Dhona has been built up already" for those who have completed ARR and "it's still in ruins mostly" for a fresh msq lv50 player... would really love if they'd figure that out) so doing that would require them to... actually do that

but having a map area? Easily doable. Release areas after the heavy traffic has died down so wedding traffic doesn't add to people trying to get their msq done and it'd work just fine, I think.