It will definitely not help. P2P trading has been requested for a long time, it even made it to the roadmap a couple times, there's also several threads opened here. The problem here is that you are using the market as a trading system, which it obviously isn't. It's a market. Just like in real life, you list a product for sale and anyone can buy it. Adding a nametag doesn't work in real life and it obviously won't work here. If you want to sell an item to a specific person there's several ways you can achieve that: either by putting it on market while both of you are online or invite him to your town and list it as a town-only sale.
Maybe make a trading system separate from the market...? Most games have it, and this one should.
I understand trying to make the game realistic, but its still a game and needs some unrealistic features to make it enjoyable.
and as you just said, for a long time it's been requested, stop ignoring your users and add it to the game.
There are annoying cooldowns for changing towns, and many people make many deals a day, and moving to a town for every trade would take way too long.
There is also trading in real life, not just a market, so why not add it, that's realistic isn't it? trading... seems like the dev team just doesn't want to add it.. since it wont earn them anymore money.. quickly start working on an even more powerful and more expensive set to sell instead of fixing real issues the game has.
Every single trade is done with both people online, the way thieves steal gear is they refresh the market as fast as they can and buy it as soon as they see an item at sale price with or without a name tag.
Trust me, if it where as simple as both parties being online to make the trade there wouldn't be so many complaints, thieves also lure people into trading with them, ask the other player to give the items first and then never give their side of the deal, its too easy to scam and steal on this heavily pay to win game.
Fix these issues and listen to your users.. stop putting off actual problems to make more stupid set that are clearly just old sets re skinned.
Respectfully
Darth.
Edit:
http://prntscr.com/f70e58