Have you considered the possibility of changing your commission structure? They way it is currently calculated by percentages is not typical of trading exchanges, at least not in the United States. To help provide liquidity, you should charge a flat-rate commission fee. Then people don't have to think about percentages, and can factor in a flat fee to their trading strategies.
As an exchange you should benefit from people trading, as opposed to just the price of Bitcoins going up. That's what your commission structure looks like now. You are making it appear that you just have a vested interest in Bitcoins just going up, up, up.