I like your system, John, and have noticed that many groups use some form of critical hits (or lethal damage) in their games.
I'm in the midst of taking some of our heroes through a Western (sans superpowers); in fact I'm adapting a module of
Boot Hill (the introductory adventure
Mad Mesa). Because of this I've had to kind of re-look at how lethal and dangerous guns can be, especially now that some superheroes who previously had 100 HP are now sitting at 4!
One interesting thing that
Boot Hill does (I don't have the rulebook, but you can tell a lot by reading through the module) is treat damage from fists (HtH) in a different way from damage from lethal sources (knives, arrows, guns, etc.). The first type you heal daily, the latter one you heal weekly (at the same rate).
Makes me wonder if a similar system might not work for V&V. It still leaves a lot for the GM to make a call on (Flame would probably be treated as lethal, but what about Lightning?), but it does provide for more dangerous damage from certain sources.