At least three people would be able to bring a level 4, at least one person a level 3. One player will bring a pregen (level 1 or 4, still TBD), one presumably a level 1 (though if everyone else is in the higher subtier, I'd heavily recommend taking a level 4 pregen).
Edit: The issue is that I've already had level 1 character deaths happen at subtier 1-2 with unlucky rolls, so playing a level 1 in subtier 3-4 will not improve the situation. While they can survive it, there's a decent risk.