I have a radical idea, not for ESO, but for MMOs in general, to address the problem of gold farmers/seller: make it impossible to trade gold.
How would this work? The game would assign prices to all items the same way they do now when selling items to vendors. This "player" price would be variable. It would change based on factors within the game. Say a lot of iron was mined last week, well, the price of iron swords goes down. The player price would be the starting point for the seller. The seller could then choose to sell the item for up to 10% more or 10% less. So if the game determined that the price of an iron sword was 10g, then the seller could sell that sword for anywhere between 9g and 11g. This will allow some leeway for the seller to undercut his competitors, but not so much that a gold seller can buy a 10g iron sword for 1000g.
The trade window would enforce the pricing. There would be a seller on one side and buyer on the other. The value on the buyer side would have to be withing 10% either way of the value on the seller side. Items listed on an AH or vendor would have to conform to the pricing structure as well.
If gold sellers can't trade gold, then they can't sell gold. If they can't sell it, they won't farm it and they won't be in the game.
Along with this system, I would make items have variable quality, like they did in SWG. So if there are 5 iron swords for sale, they might all have different stats, within a range. People would then actually purchase based on quality rather than just price.
But I doubt any game company would have the guts to make a system like this, and too many players would complain about not being able to game the AH or overcharge for their items.