Generally, with any complex human-machine interface, you want to cast as wide of a net for accommodation as possible because there are so many variables that come into play.

Like if you are putting together a basketball team, you probably want a bunch of tall dudes, but you never know how many Muggsy Bogues's are out there unless you let everyone play.

For a fighter pilot, would you rather have a female with greater ability to distinguish color, or a male that can pull higher g's? It's impossible to say what specific traits would lead to the best outcome in all possible engagements.

Even things like colorblindness can be a positive in situations because camouflage can stick out to colorblind people. Some types of deafness comes with immunity to motion sickness.