Edit: Can test in future again 
The idea is great. Embark (or Xunlai Market in its prototype version) was made just for that very reason, but for some other reason it was never implemented in the game. Centralizing all of pve trades and grouping in one huge outpost with 8men party size would be great and I dare to say, that it would greatly improve the activeness of pve for both SC players and casual ZCQ players.
However I don't think that a full transition is possible without any authority from ArenaNet (looking at you, DrStephenCW). Aside from the crybabies from Reddit there is several obstacles that could be defeated with help of somebody able to modify the game. With help of somebody like Stephen (if he's allowed/able to make those changes) the transition might happen instantly and not gradually or partially even. With some improvements to Embark, like:
- getting the "travel NPCs" closer to each other, so that the players don't have to run around the area
- giving them dialogue options to access any outpost in the game, including DoA, challenges, minor outposts
- giving PvP-only characters access to Xunlai Market, so that people can access the outpost with any given character
- perhaps a system of auctions? Xunlai Market in its presumptive mechanics, like The great exchange in Runescape (that would require far more effort though)
the outpost and the transition would make everyone pleased.
My doubts about a full change of the trading outpost might be false, but I'm sceptical that a few people screaming "yo, let's trade in Embark from now on" will be able to convince the majority.
Nonetheless I'll be there on 15th of April, good idea and initiative!
Edit: Can test again in future
It's really nice how everybody went to Marketplace
It's really nice how everybody went to Marketplace
You mean all Ether's alts and 20 other people? 
nice indeed
