I would say that security should be the top priority here so that it can gain confidence from the users. Perhaps we should really get the price real time as some of the exchanges now are too shitty slow. Not fake volumes whatsoever. I'm not really sure about the centralize or decentralise because its up for debate. Binance and OKex and Bitfinex are the most convenient exchange for me right now because they have met my criteria so far and I don't have any problems using their trading site because its fast and withdrawal is no problem as well.