I understand that something similar was posted before and success was limited, but this is a bit different.
I think that in GW2, there should be a better way to trade than finding a person and pressing a trade button. In GW2, that would hopefully still be, but I have an idea for a marketplace that would make trading infinitely easier.
This marketplace could be reached from wherever in the game at any time, like a guild hall. There'd be a special button somewhere in the UI that would take you there.
Once you reach this marketplace, there will be no people saying "WTS" and "WTB." Instead, you can bring up a window like a party search window. It will ask if you want to buy or sell. If you choose buy, a small listing of item types appears. For example, let's say I want to buy an Armbrace of Truth. I would pick the Trophies category, and then the Collector Trophies category, as an example.
Now another screen would come up. It would have a listing of bison tokens, luxon totems, battle commendations, etc. You would look at the category of which item you want to buy.
Now you'd get a window that would have a listing of entries. Each one would look like this.
[Character Name][Name of Object Being Sold][Picture of Object][Offered Amount][Average Price][Notes]
The name is if you want to pm them for whatever reason. The name tells...well, duh. If you hover over the oblect picture, it will give you its exact stats. The offered amount is exactly how much the seller wants for it. The average price tells the average of prices for this item in the past month or so. The notes are if the seller wants to tell anything else, such as "Useful for farming" or "Can be traded for Tormented items."
If you want to buy, another screen will pop up. It will have three options: Offer Money, Offer Items, or Offer Both. Once you make a proper offer, it is sent to the seller. If he/she approves, the item is automatically added to your inventory and the money is sent to the person, who loses the item but gets the money. This eliminates the "Trade" button unless you'd still rather use it.
Hopefully, you can offer more than 100k in GW2. If you're selling, a different window pops up showing all the items in your inventory. You chosse an item to sell and offer a price, which eliminates the need to shout in town until you get a buyer. Additionally, you can sell more than one item and anyone can see the stats-no more typing long-winded trade invitations!
Eventually, little offer windows will pop up giving you offers. If you accept, the item is gone but the money is yours.
I really think this idea will refine the trading system, but you will still be able to do it the old-fashioned way if you like.

Comment! I'm up for constructive criticism. Sorry for the long post.

~Chfan