Absolutely.

I have no criticism of of the mod or of people that do these mods at all.
I think they are brilliant and add a whole new dimension to an already superb game.
I imagine the balance would be very difficult and is certainly beyond me.

In history Halbs/polearms were a deadly unit and evolved out of the need to combat the effectivness of heavy horse.
They certainly decimated more than one Cav heavy army and changed the tide of battles, changed the way battles were fought in many respects.

So I agree that in game terms they need to be reasonably powerful the rest is up to the player.

If they want, stack an army full of them or be a little more historically accurate and have only a few in the army and as bondovic said have them on the flanks of the spear to deter Heavy Cav like they were designed and employed.