Lol, your in the wrong business brother. Unless your going to ante up gt;$1mio to get a seat on an exchange you will use a broker regardless of what market you trade in. Brokers in most markets give execution priority to large accounts and they nearly all operate prop desks that use your order info against you. Further, even on exchanges variable spreads are the norm. Maybe they don't get as wide as Oanda, but there's no such thing as a fixed spread.
Search for the best of what IS, not what you believe there SHOULD be.