If there was an infinite number of crit crafted armor? Sure. Getting crit crafted armor doesn't just require credits, though, it also has to be, well, crit crafted. There is only so much supply at any given moment, and besides that, not everyone will buy a custom piece just because it is crit crafted. People with the credits will want not only an augment slot, but the look they want. Some powergamers will go for function over form, but many people are much pickier than that.
Yes, but what is the point of having different types? Once a character gets to max level, the only viable gear is going to be Custom or the best Artifacts available.