To expand and clarify on the idea of defined power tiers, and how you might turn that into a way to express uniqueness.

I Could think of Knights as ranked individuals, with each rank they earn granting them the privilege of having the spell coders generate and send them custom skill crystals that can be equipped to their gear. Meanwhile magismiths or engineers as we progress could provide gear with equipable slots, and you could control our relative power tier by controlling how many equippable slots we had, and approving our skill requests.