Your salvage reference doesn't make much since to me because in your example you are changing a path of gear that you had already started on. That would be like asking to trade in your Iga Tekko +2 for Bale Gauntlets +2.

In the instance I quoted it would only provide a way to exchange currency, not a set path that you have already undertaken. When have the NPC in Nashmu that acts like a ISP currency exchange, why not extent that service to other NPC offering other currency exchange. Like I said, even if I have to go back in time to the [S]-Shadow-reign to find a banker that would exchange X,Y,Z currency then I would put in the foot work.

Asking for a NPC to exchange X,Y,Z currency is no different then the people asking for an NPC to exchange Job: slot seals.

I think the only people that would have a reason to be opposed to streamlining currency are the people that only do dynamis to sell currency. "Oh no, now all currency has equal value!!"