Done that.
The problem is, in one-on-one if somebody can get inside the blade reach, you're in trouble. A naginata is essentially a 3' sword on a 3' stick, giving you reach without losing blade length and the cutting edge. A longspear and/or polearm only gives you a short blade that is almost useless for slashing, and good for pointing at somebody and hoping they run into it. This works great in a phalanx arrangement, but horribly when you're on your own.
"Here at Ortillery Command we have at our disposal hundred megawatt laser beams, mach 20 titanium rods and guided thermonuclear bombs. Some people say we think that we're God. We're not God. We just borrowed his 'SMITE' button for our fire control system."