Surprisingly many female soldiers can keep their long hair (maybe not butt-reaching, but still). However, they'll make damn sure it's wrapped up tightly so it doesn't impede them during combat manouevers. If you check some photos, you'll see that long hair often even can be fitted under helmets during combat manouevers. When off-duty, hair can be worn "open"
http://farm4.static.flickr.com/3616/331 ... 7357ff.jpg
http://assets.nydailynews.com/img/2009/ ... oldier.jpg
http://lh4.ggpht.com/_oHF-qUKh09c/S5lCm ... oldier.jpg
http://lh4.ggpht.com/_oHF-qUKh09c/S5lDW ... oldier.jpg
So, implementing it shouldn't be that hard, as it doesn't have to be modelled/animated to be swaying or anything.