Great idea. Perhaps get some inspiration from EVE's market system. -Buy/sell orders. It not only helps create a dynamic economy, it also favors emergent gameplay, player's fulfilling the buy/sell orders for profit. -Player vendors could also have a contract system where the vendor "hires" a player to get them X item in exchange for gold or items. Also courier contracts to take items from one vendor to another could be possible. -You could also use an item search function limited to the player's current region. Really looking forward to it.