Currently, as far as I can assume, we do not have jewelry crafting in the game for two major reasons. Most content isn't scaled for the use of two simultaneous crafted sets [not to mention the ease of getting BIS without obtaining trial gear], and the fact that the end game trial gear table is structured around legendary jewelry. The following is my suggested solution to the latter issue.
The final bosses completed on Hardmode in vet trials would drop a trial monster helm [%100 chance, random trait/material, able to be traded]. Each boss from the four trials will drop one for each role: tank, healer, stam dps, magika dps. The 1 piece set bonus to these helms would give a trial buff that corresponds with the intended role of the item [dps: minor slayer, tank: minor aegis, etc]
As for the shoulders; they will drop only from the reward mail from completing the weekly trial and remaining on the leader board. The shoulder would match the weekly trial that week, would come in a random trait/material, and of course it could not be traded.
I have not decided the 2 piece set bonus to these items, and would be open to suggestions. However, these sets would need to be balanced [pve and pvp] and best in slot, as the purpose of these sets are to replace the current end game grind for legendary jewelry.
As for the first issue that I brought up regarding Jewelry crafting affecting the crafted sets, the only solution I can think of involves reworking the crafted sets to account for the probability of characters running two crafted sets simultaneously.
As for how jewelry crafting would work, I imagine it would be similar to enchanting. Once an item is created, it cannot be upgraded. That way we don't have people trying to get low quality jewelry from drops only to upgrade it to legendary.
Leave any feedback you can think of below. Thanks.