Well, you can use some kind of damage track, similar to the one in Monster of the Week. Something like: You can receive 6 soft damages before dying, or 2 Hard damages.
I don't like this kind of measurment because it seems too dissociated with the fiction, for me. You can use the Recover Moves that I showed before as a way to track the damage threshold. Maybe, instead of using them for the 7 to 9 damage, you could say that, when you receive hard damage, you are wounded and must recover. If you receive other hard damage while not healed, you die.
It might seem very lethal this way, but it's not like that. As it is said in the book, you don't need the monster to cause damage. So, if there is a character that is wounded and you don't want him to die, just use other move, disarm him, separate him, make him incounscious, etc.
So, how would that work? When characters receive damage, they roll+Protection. When they get a 7 to 9, they receive soft damage. Soft damage is a disarm, stun or a preparation for a bigger damage. On a 6-, they receive Hard Damage, and must recover. If they do not recover before receiving another Hard damage, they die.
Other characters can protect the wounded. Also, to recover from a wound is not exactly to remove the condition. So, if you have your arm broken, you can recover from the attack and continue fighting, but your arm will continue broken until you are healed.
I've had also other idea. Maybe it could have 2 boxes of damage, 1 for Soft and 1 for Hard damage (Scratches and Wounds). When you receive one kind of damage, you mark those off. If you have both marked and receive any kind of damage, you are down. You can use Recover Moves to erase Soft Damage.
If you receive Hard Damage, if the Hard damage box is already checked, you can mark the soft damage instead.
I don't know, these ideas feel strange. What do you think?
Maybe do something else? Maybe a Hard damage could mean 'out of the combat', you are wounded enough to not fight and, if you choose to fight, if you are hurt again, you die. What do you think? Or, instead of dying, you are uncounscious, I don't know. Maybe 1 Hard Damage = 'you are wounded and should stop fighting'. 2 Hard Damages = 'you are automaticaly out'.
What about these rules? What do you think?