This is an idea that I'm surprised hasn't been floated more often. It is more punitive than this suggestion, though; the HP increase between tiers is comparable to this suggestion at around 6 or 7 team members, but there's no scaling for smaller teams besides there being fewer mobs, all ATs and powers are equally affected rather than having the various provisos this idea has, and naturally with higher ranks the enemies' powers get stronger and more accurate, instead of strictly being an enemy survivability buff. There's also the issue of control effects; with every Lt becoming a boss and every Boss becoming an EB, control effects become severely weaker, to a much greater degree than anything else. That is, in fact, the exact issue that lead to me thinking up this idea as an alternative.