As a suggestion, they should do something similar to EQ2, integrating AH with personal housing.

They should have an AH, if people chooses to buy from AH, there will be taxes imposed on the items bought.
If they do not wished to be taxed, they have to go to the seller's house to buy the item.

Normally, for cheapers stuffs like crafting ingredients or consumables, I will buy it straight from AH, however, for expensive items like spell scrolls, I will take a trip to the seller's home(could be in another city) to buy it without tax.

This is a really nice system because it offers the ease of AH, on top of that, it encourages players to visits other player's house, sellers can show off their nicely furnitured home to their buyers(some 5-room homes equiped by bedroom, dining room etc really looked amazing).