I made this suggestion a year ago, but never heard feedback from devs. I'm posting this again because I just saw this picture you posted of the next patch coming out and couldn't stop and wonder why wouldn't they put this in open world for trading.
Vending Machine, you can buy it from marketplace for GC (limited 1 per person), comes with 10 slot, you could buy more slots from marketplace.
This would change trading forever, in a good way. No more scamming, noisy lobby, etc.