As the title suggests, I am suggesting a secondary mode for polearms that are usable with a shield. For example, take the Spear. It can be used with a shield in which it has only one attack direction: a thrust with extended reach, known as a hoplite thrust. If the shield is put away or broken, the Spear has four attack directions, but the thrust attack now has a different attack animation, most notably being shorter than the hoplite thrust. If the Spear had the ability to be switched to a secondary mode, it could then access the hoplite thrust without having a shield in the other hand.
For balance purposes, I would suggest that this secondary mode for all shield-usable polearms without a shield equipped
1) only allow the hoplite thrust attack direction
2) not have the ability to block (since blocking with that animation was done with a shield)
Thus, it would provide no advantage in most combat situations (as switching to access a different attack animation would leave you exposed and unable to block).
There are only a few advantages this secondary mode would offer: increased ability to participate in line battles without a shield (as hoplites normally do) and an increased reach to hit horses without a shield (as hoplites normally do). I could also envision an infantry switching to the secondary mode to gain enough reach on the thrust animation to catch an enemy who is attempting to run away.
Comments and criticisms are welcome.