I didn't read through the whole thread, so oops if this was already mentioned, but will the Korean servers be part of the JP/NA/EU servers? If it were to share the servers, then I would also be worried about the introduction of exclusive things.

Example: Running a raid/dungeon and in comes a player wearing the hanbok = potential positive/negative target that the others will focus, knowing it's an exclusive item.

If the Korean servers are separate, like how the Chinese servers have their own, then it would deem understandable and acceptable. The rest of the world is full aware of Korean culture and are fans of their entertainment media, I don't see why they would exclude this from the JP/NA/EU if Korean servers and the rest would be playing together.