On another note, I just don´t understand why they would want to postpone it themselves. I have read about the Korean military service (yes, on the Internet; no, I don´t anyone personally; Sure, everyone has a different experience and blabla) and apparently military service is an annoying nuance every Korean man has to go through. It is belittling, physically hard and everyone just can´t get over with it (apart from a small percentage who have a thing for military and would have just ended up being soldiers anyway), but it is kind of a "bonding manly thing" and everyone enjoys complaining about their military days and share those stories of "remember when your mother sent you the most delicious cake and we had it in the barracks while our captain yelled at us and we had to do 100 push-ups" etc.
But most people do their military service when they are really young, pre-university, post-university. Would they really want to be in the same group with 18-year-old boys when they are 30? Wouldn´t it just be a shame? (no offense here) Military could be a time to take off their "idol mask off" and get back to reality which they had left when they were 16-17 and joined the training companies.
In my opinion, either let them do their time properly or just exclude them from their military service altogether. It is not like the 7 of them would win the war or anything. If they want to do it, let them and now I´m talking about BTS. We can all be biased about our own preferences, but we all know that at this given moment, right now, right here, they are the biggest and most popular group and they work really really hard. Maybe the military training could be a bit of a holiday for them :D.