I respect your thoughts, especially because you have lived the situation at hand and I can also understand your points because I have a son in the Navy, a husband who served in the Army and my father was a Navy man also...plus various other friends and relatives who served our country. And we've actually had this discussion throughout the years.
It has been my experience with gay men in particular (and I'm sure it's the same with gay women) that they don't "go after" straight men. And give the guys some credence that they aren't going to leer at anyone in the shower.
If they do, they'll probably get some dirty looks and snide comments. Seems to me the proposed situation would take care of itself rather quickly. Personally, I don't think much would change if gays were allowed to serve openly. Some gays would still feel more comfortable keeping quiet about their orientation. Men serving in the military have a lot more to worry about than a gay man or woman seeing them naked. Besides, as Alyssa pointed out there are already gays in the military you might just not know who they are.