I'd prefer to be a field commander or a combat controller, though they are not listed. Field commander: obvious, they tell squad leaders, sergeants, lieutenants, and other leaders where they need to go for what reason. 

Combat Controller is similar, but much more... interactive? They're on the field with combat groups, with advanced communications stuff, and keep the platoons and companies up-to-date with the going-ons of troop movements, and to call in air support, evac, or reinforcements when needed. Much more specialized, with extra training to keep them going longer and safer, to keep the equipment running. They carry enough stuff to remotely control aircraft.