I suggest allowing players to cancel a charge attack. Here's why:
Once you've charged a weapon, you are forced to walk around without the ability to shield. This is fine and all, but if you suddenly wind up in a situation where shielding would save your life (*cough*VanadukeTheCornerRusherAndHisLoyalSkeletonLegionTrapOurHeroInACornerAndRainFiretilesDownUponHimWhilstHeIsChargingABlitzNeedle*cough*), you have absolutely no options available to you besides just sit there and get hit, or let go of the charge and get hit.
So, this is how I think it should be (if it would be) implemented:
When shielding, holding the attack button and then lowering the shield will charge an attack like normal.
While charging, pressing the shield button causes your character to move slower for a few moments while displaying a short animation, similar to the process of reloading a Callahan or beginning to charge a bomb.
After a few moments, your charge attack will be canceled, and you are free to use your shield.
I suggest this, because although such situations are fairly rare, when they do happen it's extremely annoying to know that there is absolutely nothing you can do to save yourself. I don't see any way this could be abused or exploited.
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The point of this suggestion is not to make charges foolproof, but to allow the player to stop a charge without having to actually attack.
There would still be a small period of vulnerability while canceling it. It wouldn't be like shield-canceling a sword; there would be a short uncharge time in which you are still defenseless.
Perhaps it could be a variable that changes accordingly to CTR UV's; if you just have standard CTR, you'll have a long and drawn out uncharge time, which wouldn't be any safer than just releasing the charge. With higher CTR, uncharge time would decrease.
To prevent accidentally canceling a charge attack, perhaps it should be implemented (if it's implemented) to check whether the defend key is being held at the moment the player releases the action key; if the defend key is not being held, the charge attack will occur. If the defend key is being held, the charge cancel will occur.
Oh, are you upset that you can't only use charges without consequence?
The inability to shield is what balances the charge. You can't have any reward without risk.