Meh. The Pentagon itself estimates there are as few as 29 to 132 personnel who want reassignment surgery while on active duty, and that the cost of their surgery would be less than a rounding error in their medical budget. And besides that, the military already has strict qualifications for physical and mental readiness for enlistment, so yes, they can and have always had the ability to reject enlistees. They also have strict dress codes for both men and women, both of which wear basically the same thing in combat duty, so don't see the issue there, either.

As far as your reply to another poster here who said "would you want one watching your back", I knew a female-to-male trans man a few years ago... short, but stocky, strong, and ripped as hell. I had no idea he was even born a woman until it came up in a conversation at a work function, and not someone I would ever challenge in a bar fight. I'd have no problem having him protect my country.