Women make up 6% of the Marine Corps. If women were removed from the Marines tomorrow, the lack would not be a big deal. Contrast that with the amount of work, expense, and hassle involved in accommodating the existence of women in the Marines.
If you've ever heard that statistics can be misleading, this in one of those instances. While Women Marines (WMs) make up less than 10% of the total fighting force, the instant removal of those WMs would significantly reduce unit readiness and consequently combat effectiveness.
You see, woman are NOT billeted in combat roles in the Marines. As a consequence, WMs represent a much larger percentage of non-combat, but equally mission critical billets. If they disappeared tomorrow, there would be problems and you'd lose a tremendous amount of mission competency and overall experience.
To be honest, I've had WM's in my subordination only twice while I served, and that was while I was assigned to I&I duty. It wasn't that bad, although I'd by dishonest if I didn't admit there were some ancillary issues you just don't have in an all male environment.
I think on balance, WMs bring more the the Marine Corps than they cost.