At the moment we don't know the uniqueness of how sub fractions will play. Its all speculation. Till we get more info we can;t argue that 16 slots isn't enough.
we know: for example space wolf don't have apothecary but wolf priest "JR" as base class. blood angels will have death company as elite. basically if you want to play all the classesyou need 20 slot. and in the future we have more sub faction and more faction. in FF14 your character can use all the classes for example, this is why there is only a slot.
