In the current market for trading resources you have no idea who's material you are buying or selling to. If a country or player identifier was included on the screen for "All Trades" one could be more selective in their trading choices. So for instance if Turkey was attacking Greece you could purchase Greek goods listed at a higher price or sell to Greek requests at a lower price to help support the Greek resistance. Conversely if you are attacking or defending versus another player, why would you buy their goods or sell them resources they need? Under the current system you have no idea who's goods you are purchasing or selling to unless it is a negotiated trade between 2 active players, so you tend to buy the cheapest available and sell to the highest bidder. If adopted this suggestion would add more depth to the economic aspect of the game.
Pete