Which masters degree would most help a career-oriented maneuver officer (I assume something along the lines of a MPA, but open to guidance)?

Look into something that will benefit you in the civilian world after leaving active duty. Promotion boards generally prefer that you have a masters degree, but not necessarily in a specific field.

You may think this crazy - but Masters in Systems Engineering would be applicable

Do one that interests you and remember, the time we serve in uniform is usually small compared to the time we spend out of it. Career oriented just does not mean you always focus on your job in the Army but a job after the Army. If you focus all your civilian education on what you do in the Army, what will it do for you at age 46 when retired?