McCarthy seems to have the right experience, 75th Rangers, which although as an organization they have come to be a symbol of the best a regular force offers short of being "Special Forces".  He should have appreciation of main land and special forces.
He is an Afghan Vet and has done well in the private sector.
He also does not seem to have the sort of baggage that is said to have stopped two prior nominees because he is identified as a Christian by LGBTs.   
The biggest task an incoming Secretary of the Army may face is man power shortages .  Some analysts claim a draft  is the only solution.   
Those pushing a liberal agenda in the services none have asked or are afraid to ask if that has hurt enlistments,  also the demands placed on mental, physical and other standards like beig drug free, has been a problem; I have to wonder how a draft could fix?
A draft will result in activism against the military. Since the end of Vietnam and the anti-"war" mobs have not protested.