Adding an entire merchant might take some work, but just tweaking the inventory of merchants who sell crafting items should be easy enough, I imagine. We simply need to add more stuff to their list of possible items.
I remember when I was in Arx and needed to craft some big potions, IIRC. I needed to start from the minor potion, and it required Augmentor. But by that point in the game there was no basic Augmentor to be found anymore, and no one sold them. I could have as many best quality Augmentors as I liked, yet they couldn't replace the basic ones. The irony.
