There are men and women that serve together in other units where they don't have issues with discipline and unit cohesion. These have become excuses and fall backs for keeping gays out of the military and off the battlefield. If you believe this, then show proof. Don't just state that it is fact without something to back it up. And you need to include how women and gay men would cause the same discipline and unit cohesion problems if you are saying that they should be treated the same as far as keeping them out of certain MOSs. As I have stated, there are plenty of reasons to keep women out of combat, and I'm sure that I can find some studies to back this up. Gay men already serve in combat units.
I highly doubt that very many soldiers will refuse to billet with other soldiers due to their sexuality. A few may have problems with it. The thing is, they are doing it now. Also, if someone is refusing to share quarters with someone, isn't that their issue? Aren't there ways to deal with these things already? I'm sure there are some racist guys out there who don't want to share quarters with guys of a different race, but they still have to. Why should this be different?