Strange Mechanics: Success & Effect & Location

    I think it was the old Top Secret/SI game that had a mechanic I liked.  You rolled percentile for success, and the ones die was your hit location.  The torso was 0 and the head was 9, so the only way to hit the head was to roll kind of high and yet still under your skill total, which made it fairly tricky.  I have always liked this system (though only played the game a few times, way back when) since it combined the hit location with the success roll.  For some reason, recently, I have been thinking about it again and wondering if you could add the effect as well.
    So, you have a 50% skill for attacking someone.  You roll.  Anything over 50 is a miss.  Anything under/equal to 50 you look at both dice.  The ones die is your hit location (0-4 torso, 5-6 right arm, 7-8 left arm, 9 head - for melee, which focuses on the upper body).  The tens die is your base damage (so from 0 to 5 max, since your max skill is 50), add your weapon's damage modifier on a hit.  I'm also thinking instead of exact location, you could just use coverage in general.  So maybe everybody/thing who takes critical hits (after all, a wall doesn't really care where you hit it at) takes a critical on a 5-9.  But someone wearing a half suit of armor reduces that to 7-9, and a full suit is just 9 only.  This lets the GM choose where to make the hit land depending on the circumstances of the fight instead of looking up a table.
    There are two ways I'd modify this.  Some things alter your base skill and some things alter your actual roll.  Most modifiers would be to skill, increasing or decreasing your skill level that you have to roll equal/under.  So, close range might be +20% while high wind might be -10%.  Simple.  But, some things would modify your roll, that is, the number you use off the dice.  So someone who is vulnerable to your weapon (silver, fire, whatever) might be a +5, or, add five to your tens die for damage.  An aimed shot might be +3, adding three to your ones die for hit location (or maybe just letting you move it by three points towards wherever you were aiming, depending on general or specific locations).

    This gives you three different measures off of just one roll.  Which has a nice feel to it, in theory.
    The thing is, the more I play with math and different resolution systems the more I wonder if percentile isn't just a better option.  Having the odds out there explicitly seems nicer than making the player do mental mathematical gymnastics to decide their chance of success.   Granted, I do like the bell curve, and the Fate-like systems that go +/- your base skill, they do give an intuitive feel for where you generally stand (since it's what's on your character sheet).  But I keep wondering if a simple percent-based system might be the easiest to understand and use, and if you could also get some extra information out of it, like with this system, it sounds even better.  I don't know, just something bouncing around my head.