If your plan were to be adopted there would be no need to ‘clearn up the pentagon’ since by stopping all discretionary spending you would have completely closed the pentagon. (Defense is included in discretionary spending.)
But “defense” is among the enumerated powers. Can’t eliminate it all if we adhere to the Consitution. Cleaning it up does not mean getting rid of it.
In the history of Ft. Huachuca, Arizona, the fort was originally an outpost but grew with importance with the containment of Geronimo and his band of Apache. It was also responsible for the security of the border with Mexico and played the key role of General Pershings pursuit of a cross border raider known as Poncho Villa. My point is this does not violate posse comitatus in that the military is providing for the common defense in its actions to defend our border from foreign invaders.