Cool. And I think a comparison with sneak attack isn't such a bad thing, especially if you look at it as part of an extra damage technique common to rogues, scouts and fighters - it is the triggering condition that alters from class to class, much in the way I see your passive perception concept...
Quick question...how will punishing blow interface with thrown/missile weapons?
I could probably answer this myself by digging through the collected threads, but I'm new to Trailblazer and am in the process of digesting your changes [which, in the main, look like pretty elegant compromises...