I once suggested a "Shields Shall Be Splintered!"-ish mechanic for injured limbs. Basically, let the player decide when an arm or leg is injured, in exchange for avoiding outright death. Adds some detail without extra dice rolling or modifier finagling.
Can we do the same for stuck weapons?
If a PC hits an opponent with an impaling, the player can opt to do an extra die of damage in exchange for losing the weapon (it's stuck and torn from the PC's grasp.) Make the decision before rolling the die. Similarly, the player can opt for an opponent's weapon to become stuck in the player's character, disarming the opponent; this decision must also be made before the die roll, and on 5+ damage, the GM rolls an extra die of damage.
Additionally, or optionally, the GM can rule that impaling weapons get stuck on a 5+, whether the player desires this or not. In this case, the stuck weapon is only torn from the attacker's grasp if the attacker's Strength is less than the defender's Move.