I like the idea of instead of multiclassing you get more specialized in your single class by gaining extra archetypes/etc.

I'd consider this for something like a Cryptic using something silly like the Aegis trained s-class archetype. Not sure about the otherside, if it is gestalt. Maybe an akashic class? I find myself recently being more partial to them. Maybe a Promethean? Snag this as my free archetype?