Yep, M&B combat system actually limit a lot of actual weapon usage. Polearms in particular suffer a lot from this and lost tons of versatility, the way they are used now hardly represent reality.
Having the ability to change grip and stance would be a good step to address that. We already have a dedicated button for changing weapon mode, but it is so rarely used, aside from couching lance. Give us more things to do with X key, a lot of weapons can benefit from this. For example, one-handed spear can have 2 grip modes: the current Underarm mode with more reach and Overarm mode with less reach but more comfortable for close melee.
In fact most artworks depict spearmen fight in formation with overarm grip, since they can stab over the head of their allies and over the shields of enemies right at their face and you have more room to move your arm and spear.
And by Overarm, I mean actually holding the spear like you are going to throw it but thrust with it. However it might be conflicted with throwable spear. Arghggh.. see what I mean about the combat system limit?