Now that the mod is porting to 1.16.5, certain factions should absolutely get the Piglin Bartering System!
The ones I have in mind currently are the Lossoth, Northern Orcs, Half-Trolls, when the Morwaith are split into Subfactions then the Southern and Western Morwaith (Eastern and Northern Morwaith would trade coins), and possibly the Taurethrim?
Not sure what they'd barter with, but I really don't see the Lossoth, who "did not value jewels", trading for items with silver coins. I made an exception for the Eastern and Northern Morwaith because the Eastern Morwaith are known for trading Mumask to Near Harad and the Northern Morwaith are known for being bought as mercenaries to fight for Near Harad, so I could see them using coins.
I also considered Dunland, but I'd like to hear y'all's opinions on that first before saying anything.