...It's been 4 years or so since I've read the core rules, though, so I'm not sure how I'd do it. There really just needs to be some combination of additional condition statuses / flow that makes every combat check more meaningful.
When they introduced distracted and vulnerable as conditions in SWADE, I thought they missed an opportunity to have a tighter, interlocking mechanism between shaken, distracted, and vulnerable to make fights more strategic and less reliant on just rolling high numbers
Frankly, I'd probably just bite the bullet and implement something along the lines of the way Genesys does it with separate fatigue track equal to the character's spirit+vigor, and then a "crit" table to cause wounds once the fatigue track reaches zero. Fatigue reduces = damage rolled on all attacks that don't cause a shaken condition or wound...