I don't have any experience at all of the army, raf etc but I do have experience of high performance athletes in a power based sport.
I think the physical argument is a bit of a red herring. I am not saying that on average men aren't stronger than women just that women can be stronger than men and the strength required might be over rated.
In society at the moment (and this is a huge generalisation) women are not encouraged to be competitive, use their strength and partake in physical activity to the same extent as men. Women are therefore starting from a much lower point on the scale and so it is understandable that not many women would make the grade.
The level of expectation for women to perform is not as great as it is for men - so a lot of women will, naturally only perform to expectation as that is all that is required.
Those women who do break the mould and focus on getting to the top of their chosen sport end up being faster, stronger and more powerful than most of the men involved in their sport. I realise that this is still a small percentage but it does show that women, if encouraged can gain similar strength to normal men.
Anyway what I am trying to say is that if the tests for women were the same as for men some women would be able to pass them. In addition if women were encouraged more, from an early age to use their strength, be involved in sport etc that the numbers of women achieving those levels would increase.
In addition, I do not doubt that warfare is physical and although there are some tasks that would perhaps take a great deal of strength, stamina would probably play a bigger part. There is very little evidence that women have any less stamina than men. In fact when it comes to extreme events e.g. 100 mile runs etc, there is some evidence that women may even have more stamina than men. For those tasks involving extreme levels of strength then teamwork might be better deployed.
And whether a man or a woman's head is stuck another's crotch when you are in the middle of a battlefield is just weak. You really think that men couldn't dissassociate themselves from "their sexual urges" in that kind of situation? Whether they choose to is another argument. And how often, realistically, is that likely to happen (quite prepared to be proven wrong)? But surely it is all about teamwork and using your resources in their best positions (literally in this particular scenario).
However, on a very personal level I cannot get past the fact that everyone in a combat role is trained to kill another human being and I would rather not be the one doing the killing or the one being killed. So I would find it impossible to be part of it and perpetuate the violence that some men do.