How about another idea that come up over the weekend. LET’S STAB PEOPLE!
Deep Stab. As an action you can expend one superiority die to deeply stab your weapon into the target of a melee attack. If the attack is successful, you drive the weapon deep into the target. You are considered . As an action the target or a friendly target can attempt a Strength check (DC equal to your save DC) to remove the weapon. At the end of each round that a target has a weapon stuck inside of it, the target takes damage equal to your superiority die. The target is considered to have armor of the same material as your weapon for all effects a spells.