Also if it was moved to MS roulette it'd be a different # of people in the ready check, so the moment you had someone back out you'd have a bunch of others doing the same. Basically party up with 1 other person, queue pops, 1 person confirms, tells 2nd if it's 4 or 8 people, 2nd person backs out if it's not the one they want.
tl;dr bad idea to put it in main story roulette.