Saxman,
There you go again.  You have it in your head, wrongly, that the damage model in AH unfairly favors cannons.  It doesn't.  You somehow think that a more realistic damage model, something I'd like to see too, will lessen the the firepower difference between, say, a Spitfire Mk VIII and a P-51D.  It won't.  The Spitfire Mk VIII has noticeably more firepower than the P-51D and a more realistic model will not change that.
As to your anecdote, was it a bullet hole or a gaping hole blown by a cannon round?  I was referring to bullet holes.  If the airstreams traveling above and below the wing remain separated then lift will still be generated.