Well, the main argument that I've heard against women working in combat roles such as infantry is for personal hygiene reasons.
From my understanding the submarine is a tough and unpleasant environment.
I think it's a recipe for disaster. Personally, you could never get me to stay on a ship for months at a time.
It's as tough (tougher) mentally as it is physically. It definitely takes a certain temperment, and I don't see a whole lot of women having that sort of disposition to want to seal themselves up in a steel neutron-powered sewer pipe for 70-80 days with no contact with the outside world.
Oh, and the first girl that dropped a TDU weight, can of flour, wrench, whatever...you get the idea. Damage control? Yeah, I'm gonna let little Susie non-qual get into full FFE gear and try to pull my unconscious ass out of an Engine Room fire. Oh, and lugging shore power cables across the after brow and hooking those bad boys up in the trunk, to say nothing of having her try to reset the pressurizer startup heater breaker. Ah, good times.
Like I said before, women can do most of the actual JOBS that we perform on submarines, but not in a submarine ENVIRONMENT. That's the problem the CNO and SecNav don't quite get.