Thinking about severity a bit more ... I think what I was trying to convey earlier can be summed up by this question: If my worst injury is a broken finger, then why did I fall unconscious and nearly die? That's what's been nagging me about some of the minor injuries. They just don't seem consistent with reaching 0 hp.
I still think they should be possibilities, because if severe wounds are possible then it seems weird to never have combatants receiving minor wounds. I like your idea of the minor wounds being the result of a critical that doesn't drop you to 0 hp, or maybe other criteria. Like dropping to a quarter of your total hp, getting any wound that delivers more than 20 hp, rolled after the fight by anyone who takes hp damage, maybe rolled anytime the GM wants to add some color to the fight. Any of these could be presented as optional house rules, too.
I've also been thinking of that video you posted recently that talks about people taking serious, even fatal wounds and fighting on for a time before collapsing. Is there room for that idea in here somewhere? That could be an interesting take on the Diehard feat.