When people think and write about "The Military" they often use combat references. The fact is that around eighty percent of people in "the military" never serve in any kind of combat environment. Most are technicians, administrators, and other "support" type personnel. The U.S. armed forces employs people from all walks of life. That includes racists, rapists, thieves, closet homosexuals, outright bigots, and borderline psychotics. There is no reason not to add transgenders to the list.
I agree with your reasoning but all the people that are serving in active service, that went thru boot camp, are subject to combat service if called upon to do so. It is what you signed your life on the line for. Make no mistake about it, If you are ordered to combat - you will go to combat, no matter your designation.
If you have no will to follow your orders, you should be removed/not accepted. Orders are not subject to acceptance. Its not a matter of asking will you it is a matter of telling YOU WILL.