Currency exchange,auction house

The idea is that u can sell currency between players, u put one guy in shop where players can sell currency like in market for example u put u want to sell 100 mc for 5000 gold, or u sell 5000 gold for 100 mc, or 10 cc for some gold etc...Other thing is auction house, market is all well and good but i think the auction house could be fun, u put an item for auction u place starting bid, and u can  choose to put item for 1,3 or 5 days for auction.When u bid for an item the amount u bid is automatically taken form u and if u dont have highest bid at the end your gold is returned via mail system, if u have highets bid seller get his gold via mail and u get item via mail. House can take some % of total sale,and u can use scrolls to lower that %. There is always the problem for snipers on any aution so i have a suggestion whan a time counter gets to 5 min before expiration it sholud just say less than 5 mins.