Where a genuine requirement to run 100 meters, pick up a 180 lb man and carry him back 100 meters in 60 seconds exists, those requirements should remain.
However, nature has conferred different strengths and weaknesses to men and woman. Both sexes are able to do some tasks naturally better than others. Feminists won't admit this but it's a fact.
The military probably already has considerable information pertaining natural abilities of men and women. Where raw strength and endurance is not a requirement, the best teams may be obtained by including men and women. Fraternization is always a concern in such situations and the most practical mixed sex teams may be those where at the end of a mission, everyone can go to their separate quarters.
In situations such as flying frontseat and backseat in a combat aircraft... especially helicopters, the generally better ability of a woman to multi-task than a man may make male-female pilot tandems a better mix. The male has natural aggression, risk taking, orientation and an ability to focus while the female of the pair is better equipped by nature to simultaneously monitor instruments, communications and maintain situational awareness.
Even with fighter aircraft, my understanding is women are generally better able to withstand g-forces than men which again, may give a male-female pair an edge.
Got a link? The only study I have seen shows female performance in high g environment is 15% lower than males with significantly higher risk of neck injury due to bone and muscle structure differences.