It is weird that FPS games so rarely have female player models.
With Brink's art style and costume options it could be pretty boss.
Maybe in Brink 2.
I'm not a chick but here's how I see it. While I'd be all for it, there are a few barriers which might take extra thought to overcome. The art style for females could go two ways, each with a con. Either the females will need to be ugly to match the style of all those giant-nosed male faces, which I don't see being a popular idea, or they'll end up being ridiculously sixified for sales and subtract from the original games art direction.
Secondly would be the excecution of body-types. As we should all know, women on average have thinner frames. The medium and light body-types of a female would be harder to differentiate for the mediums already skinny physique. They barely got away with male lights not looking malnourished. And then there's the heavy body-type. They need to take steps to make the characters hitboxes believable and fair to their gender counter-part. A muscly woman couldn't get that freakishly bulky and retain any sense of reality. An obese woman of the same width wouldn't be put with a squad whose lives rest in her hands. Even if it went through, to see the sight of some female giant running through a battlefield, even if only occasionally, may bring some pretty comedic reactions. The developers may have thought that they may cut off a large group of people from giving heavy a try just because they didn't want to sacrifice the more attractive female aesthetics, whereas they wouldn't mind so much to try out some lard-arsed, beefcake of a man. Afterall, unless you make an entirely new character, you're stuck with your gender.
Thirdly is a point you can blame purely on men. Not all men, but a big enough group that it comes closer to a stereotype than a niche. Those men that primarily opt to be female characters over male. They're suprisingly abundant to the point where the presence of female characters (note: no longer presumed actual females until proven otherwise) becomes cringe-worthy as opposed to welcomed. They'll use it whether the "I'd rather look at a females ass" excuse is on hand or not. It's only my personal preference however when games male:female ratio are a bit more believable.
When few women are combat ready alongside many men, it raises a point about those women being tough. When there are just as many men as there are women, it makes the males look a bit redundant in their protective nature.
Maybe their reasoning for no female characters isn't as clear as for a game like counter-strike. For that reason they would stay tight-lipped if it was for atmospheric purposes. And of course companies aren't going to jump at the opportunity to tell their fans if instead it was low on the priority list during strict development times.
Finally on a smaller note, some voice acting will have needed line tweaks where characters refer to he/she. Particularly where the Resistance often refer to their allies as brothers.
P.S. Yes I do feel I may have stepped into a sixism minefield having typed this but it's not the intention.
(Checked maybe for Brink.)
P.P.S. Sorry for the wall of text. TL;DR Just reasons I see against, mostly (but not totally) as it would be seen from a developers point of view.