Bartering, IMO, would be nice to consider, but I would rather see a full blown economy. Supply and demand should be implemented and arbitrary value (this item is worth 100 gold) should be tossed out the window. Scarcity should be real and abundance should be plausible.
I.E. if you invade the mine, kill the workers and burn the equipment, the abundance of that product would stop increasing. In the case of iron, the whole tools industry would be turned upside down, but as the price of equipment (weapons, farming implements, building materials) goes up, so do the things that were produced using those (mercenary wages goes up, soldier pay drops as states have trouble affording their equipment, food and housing increases, etc.) Obviously, people would notice and would rush to fix it: whatever government exists sends recon then if necessary an army, then rebuilds the mine and eventually things return to normal. This gets more interesting when you consider dragons are said to be free roaming and terrorize the country side.)
Currency should be capped. As in there is only so much gold in the world and it is only mined at such and such a rate and only so much has already been mined. Many games just create wealth without considering where it comes from or where it goes when you sell it. In oblivion this was apparent when bandits suddenly had glass armor everywhere.
The effect of this was that the player got rich and the real value (the value the PC assigns to gold) drops. I think it would be interesting if having masses of gold meant you really were rich (buy the mine and stop production if you want instead of raiding it. would lead to whatever people used the produce would not have it. As in that group gets their weapon material 'there' so buy it and shut it down = they don't get anymore weapons.)
Currency should be capped (again). Consider games like WoW. At higher levels money becomes trivial, anyone can go out and loot for a few hours and make a million what becomes truly valuable is the items that drop very rarely. And in this way gold becomes a non-currency and is replaced by items -- it's not "ill buy that for this much" it's "ill trade you for that". If you eliminated "drops" as it is and said "there are only so many items" (adjusted as people join / leave the game) gold would instantly become everyone's first priority. because with enough you could buy what you wanted. Instead of just finding it in the auction and hoping you would get lucky. Furthermore buying things like supplies (potions) would be less trivial as there is not an infinite supply. you would have to struggle to manage resources.
Back to Oblivion, if you as the PC can easily get as much gold as in the count's entire estate but you cannot spend it (there is nothing you want to buy that has similar value -- you have infinite money), then are you rich? Or is he poor? Is gold really valuable? To you?
This is especially possible as TES5 is a 1 player game AND because of radiant AI.