Why tho.
The way they work is too random to my taste. I donīt like the way a novice weaponsmith can forge a weapon that far surpasses the best masterworks from legendary weaponsmiths, for basically no reason.
I have been thinking about that too. It would be nice if moods were only (or mostly) had by experienced craftsdwarves who could be believed to exceed themselves in divine inspiration. The reward then wouldn't be a skill boost, but rather a game-changing artefact. Of course then the artefacts would have to be more powerful in one way or another.
To keep in topic, I've had only few memorable artefacts like a candy axe finished just before opening the circus or a platinum throne for the king who likes platinum. There have been few really frustrating items where the material and the item type didn't really meet, like that one haunting artefact combo of two consecutive Weaponsmith moods producing a candy war hammer and a golden sword.