Khan will be banned, not because of centralization, (thats not why we ban mons) but because of these reasons:
A.) Its speed tier is 100, severely limiting what would counter outside of priority, meaning that what would counter it has to faster than it, requiring a scarf or priority to survive.
B.) The above, combined with it's bulk and sheer power means that a lot of frail fast mons that out speed it, such as Keldeo, can't 0HKO it thanks to it's bulk, and are destroyed when it hits back. Its power and bulk, combined with it's speed make to too much to be revenged easily, or even just taken down.
C.) To revenge it, you mush sacrifice something to do damage, then finish it off with priority, or switch in one of it's counters, Confagrious, dusclops, or whatever, because it will kill them with ease if the don't switch in safely. To remove it from the game literally requires you to sacrifice something. Even with the rocky helmet sets (which have been around forever, seriously, do some research) you still have to sacrifce a mon to kill it, with something ferrothorn, dying so khan can take a bunch of damage from hitting thorn, then being finished by priority.
D.) For example, one can pack a threat that is checked by the same things a M-Khan, and once say, Rocky helmet G-Chomp is dead along with Khan, that threat can sweep and win.
M-Banette's prankster destiny bond is awesome, cause i can pick and choose a mon to kill. Just gonna say it, even if this is the Khan thread.
And you a have a khan whos attacks BOUNCE off the def ghost, because of Khans terrible attack outside of Mega form. Normal Khan sucks, its attacks can't break ghost type walls like Dusclops, sableye and confagrious. Boing. Now your burned.