Once you have a single crafter who's mastered everything, what's the most efficient way to raise up another?
Having the first make items for deconstruction by the second uses up materials. If those are higher-level than they use, they won't get the mats back. It they're the same level, the two crafters are competing for the same materials. If they're below, then the junior crafter doesn't get as much inspiration from the piece. So which is the best bang for the mats?
Dropped items get sent down anyway, and don't really figure in this choice. Although if the trait is unknown to both, there's a separate decision on who researches first. I usually find the higher-level crafter has research pending and the lower one will be able to do the research and send up a cheap piece before a slot opens.
With multiple high-level crafters, I'd expect the flow of lower-level mats from them to make all this a bit moot, so it's really all about that second one.