40k is a pathetic (by the very word) fantasy for little pre-pubescent boys (who like to attach paint on overexpensive plastic).
If you read one its rulebooks, you get the notion that the futurist movement, which idolized war, manliness and pathetic dying for blood, honour and shit did actually survive the trenches of the First World War.
The fact, that there still is melee in "modern" combat is preposterous.
Ever heard of Technology?
Ever heard of the invention of the Tool?
Technology, tools and the hand with the antagonistic thumb and fingers enable humans to surpass any animal in strength, armor, speed, lethality, etc.
Your question is a bad joke.
I mean, have a look @ Africa, where CHILDREN are soldiers... no, not fully grown humans (be it male or female), but CHILDREN!
The invention of the assault rifle has made this possible.
Whether a society, where children fight is desirable is a question that is not part of the pathic 40k world, which consists, as someone already put it entirely of "fight and death" (add: "shitloads of pathos, pathos, pathos") - and there you have your answer.
A woman in an exosuit/armor with a helmet on would look EXACTLY the same as a man. If you consider that movement is assisted by technology, there would be no differences - regarding combat capabilities - left between the 2 sexes.
But then again... there goes your little boys' fantasy, which can best be checked in American cartoons (take Batman for example and check for the picturization of the average male vs. the average female, what do you find?) and latest macho video games (Gears of War, anyone?) where males _have_ to look like 3metres tall, 2metres wide, 120% muscles and women like 40 kilos, 2 pounds of make-up plus cup-size F.
Did I already mention that the world of 40k is pathetic?
