I think for most of the military specialties (primary care related) COMLEX is enough, besides rotating at the base where you want to match into (if many locations exist). Also, if you rotate where the "consultant" per that specialty is stationed, that can help too as they go to the board as well (consultant is the the person who reports to the surgeon general per branch about the state of that specialty in said branch). Also, I think one program director per specialty goes to that board as well, would be nice to get face time with them. But I digress.
Anyway, I applied for a competitive specialty (ortho) and the program director told me point blank that he was glad that I took USMLE in addition to COMLEX and that it will help me not only in the military match, but clearly in the civilian as well. This is all contrary to what everyone else had told me. Also, you never know what will happen the year that you apply for the military match. Your situation may be better served in a civilian deferment and the USMLE will help you in SO many ways. You can never predict the future.
Lastly, I think despite the nebulous point system that they have in place, there is some wiggle room as well. If they have one spot for civilian deferment between two applicants, I have to believe that regardless of the "points", they'll give the deferment to the person they believe will successfully match in the civilian match. For most specialties, rocking the USMLE will greatly help your application in additiont to COMLEX.
Just my experiences.