Here is my current idea if anyone could give their appreciation:
- define the dice pool as conventional dice pool definition subtracted by an extra layer of difficulty (eg. -2);
- then, if the player scores at least one success dice after the penalty, the damage they deal at the end would be total number of success dice + a damage bonus modifier (eg. +3).
This is how Chronicles of Darkness combat works. Unlike in the classic World of Darkness (20th anniversary edition and before), nothing ever changes your target number: it's always 8, 9, and 10 that count as success. Instead, increased difficulty is represented by decreasing your dice pool.
Note on probabilities: 10s explode, so the expected value of a single die is 1/3 successes. You can simulate this with success being a 5 or 6 on a d6.
In combat, these dice pool decreases can come from your opponent's defense and generally being distracted, among other things, but also from making a called shot. But a called shot that succeeds can inflict various status effects (known as "tilts") on the opponent, such as a hit to the eyes leaving them blind, or a hit to the wrist disabling their hand. And sometimes, a called shot to a monster's weak point could increase your damage modifier: a flat number of successes added to any successful attack.
The result is that a called shot to the weak point is less likely to hit (fewer dice), but more damaging if it does (extra successes added if you roll at least one success).