Well folks, I think this is almost on its way of making it public, so, one final question!
Global server owned shops where you can convert extra resources for money to buy land and other surprises?
Advantages - No fuss to players to setup a shop, shop always buys your garbage, available globally via commands (not to many, just /shop)
Neutral - prices float
Disadvantages - IDK
Localized player owned shop
Advantages - Players control the market prices
Disadvantages - Player shop may refuse buying all the extra garbage (dirt, cobble)
Personal opinion, global shops are easier and are a lot simple to maintain.