One of the main purposes of the braces is to resist racking of the frame due to wind loads. Parallel to the bents, there is a much larger surface area of exterior wall to catch wind like a sail. Perpendicular to the bents, there is only the end wall to catch wind, and the braces in several bents to reisit that load. The braces are generally not as heavily loaded and it is possible that one set can be omitted without compromising the stability of the frame. This can be checked with an engineer's analysis.