As we have learned over and over human bodies adapt well. Unfortunately, we have also learned that so do viruses. The problem with your idea is not that it wouldn't work (though it would have bugs that would cause other side-effects and be a royal pain to maintain), the major problem is that crackers who write viruses can react to what we send out. They're not going to sit back and say, "oh well, there's no way to defeat that anti-virus software". They're going to get in the middle of it, take it apart, and build something that's immune. Just the way viruses want to live and thrive so they adapt.

Not that we should live in the stone age, but upping the scale of viruses because we tried to create a better anti-virus doesn't sound like a good idea. Maybe in the far future when we have quantum computers that can handle the load of vicious viruses and anti-viruses duking it out constantly such a thing would be feasible. Although then, there would be more shades of gray then 0 and 1 and we could also get a close-fit system working (in theory).

Really, it all comes down to:
Make an idiot-proof widget and someone will make a better idiot.
-or-
Make a hack-proof widget and someone will make a better hacker.

HTH,
jynx

NOTE: thanks to all above material for thoughts :)

update: re-worded quote after thought about what good words to use would be for the re-wording...