I would like it if items that are connected to unimplemented professions could be obtained from NPCs that are practicers of that profession. The mechanism for it could be repeatable quests where the NPC would take set amounts of certain items and tria and then "make" the player those items. That would both allow the player to have more than one but also limit how quickly new items could be made and keep it from becoming just a bunch of stray litter.
An example would be giving Ondren a Ruby, paying him tria, and then getting back a simple cut or an ornate cute ruby depending on how much money was paid. Perhaps kra tells you to come back later and you pick up your gems after delivering the goods. Then you have a lockout to prevent you from turning kra into a cut ruby mill. Might also help if the amount of tria you can sell the item for is close to the amount you pay to get it in the first place.
I would really like to see NPCs provide parts as well. Cut gems, plan bands(for rings), streched canvases(for painters), unglazed pots, Empty bottles, etc. That would help people RP specialization as well. For instance, my jeweler will make rings and set gems into them but he won't cut the gems himself. That leaves room for a gem cutter character to come through and provide cut gems. Both can make use of an NPC providing cut gems. The jeweler can use them in RP preceeding finishing a piece of jewelry and a gem cutter can use them for providing wares to supply other players.
The idea is that this will help people RP a more diverse set of skills since it would provide them with items they need without having to wait for engraving events or having to come up with books on their own. Taking out the extra steps might encourage more players to spread out by making it easier to do so.
That being said, I know that this would be a lower priority so it is something that would be nice to see in the future.