That's where the job gets a bit hinky, since engraving would cover various items, from rings to armor to misc little items. And the job is more of a rp aspect and flavor then something that can give a bonus in game like the other jobs so far. I think it would be fair to allow a Engraver to do both, being stationed in Port, with expensive materials, seems like a good draw back to it.
Also it would mean almost every other crafter would have to seek out a Engraver, or begin learning the art as well, if they wanted to add a higher quality to their items. I rather like the idea of several crafts coming together. As well as seeing more items with flavor to them, not just countless steel fullplates grinded out. As well it would give more rp between chars when someone orders something, they could sit down and discuss with the crafter what they are looking for.
Also be nice to be able to take in items found and have them worked on by craftsmen and have them altered to you're taste. Also would be a nice gold sink with expensive materials to do such.
It would be best if we could create a different material and cost per base item style but i'm not sure how you could make that work and then it seems like there would have to be a ton of different materials to cover all the possible items you could craft. I'm guessing it be easiest to make just two base materials? One for names and one for bios, Bios being the more costly one.