Personally I would like it to be an Auction House not a buy it now for set price only with no bid history. Should be similar to what you see in World of Warcraft with some tweaks for economic balance. I would like to be able to put a minimum bid price and a buyout price on the item if I want. So I can at least get the minimum amount I want to sell the item for if someone bids on it or get the full price if someone wants the item right then and there. Pricing history shouldn't be here because that is what allows RMT to take control of the market by changing the prices for everyone to see and some people step into the trap, generally fansites will have an estimate buy out price average for all servers combined (or you could use the Lodestone),and this would work for SE and the fansites for SE went around to all the big named fansites and did a face to face interview with them and approved their support.
What I really do not want to see is what they had in FFXI and they called that a Auction House. Nothing about that was an Auction House except for the fact that you went to a "Auction Counter" of sorts and could see all the items that other players were selling easily.