My thought about a lot of the women looking sexy is that usually all the guys are not too bad looking either if you actually pay attention to the full picture. I"ve heard this discussion before in reguards to the skin hugging suits that female superheros wear, with their objectors being all the while oblivious to the fact that almost every male superhero ever has worn a skintight outfit that doesn't leave much to the imagination. Batman even has muscles carved into his armor, and in at least one movie with nipples on his armor for no reason other than sexual appeal. (The one with George Clooney)
Dr. Manhattan even goes full monty for some of The Watchmen (even if his dong is CG) and we find noone really cares.
I think a lot of this is is projected sexism from people who ignore men and who only focus on women's sexuality. Maybe it's just safer to make it clear that each sex has optional sexy clothes they can wear. Maybe even call the sexy clothing the same thing so it's clear. I do agree though if it's not possible to opt out of having sexy clothing but we have to make a distinction between sexy models wearing it and the clothing being flattering.
Having said that, the picture at the start of the post from Mass Effect does seem rediculous. I wouldn't have minded not having the chest pressed flat with armor like she would in combat gear, the point would be that futuristic armor is form fitting and doesn't always work using plates. However the shoulders just beat the crap out of that idea. Giant armored shoulders over form fitting bewbage. Yup, that's pretty bad. Like her shoulders are the part of her she's worried about protecting. Unless those shoulders are shield generators it's a bit over the top for futuristic military fashion.
If there are sexy outfits, please at least make them suitably unprotective and not some kind of tassles of arrow deflection setup. Maybe even add a charisma bonus and be up front about it. It might actually make for a good example if some of the "unrestrictive" male outfits were clearly meant to be sexy. There's more than one way of not being sexist and they all involve treating everyone the same way.