If someone doesn't understand how to use the basic metric system they need to go back to the 1st grade and learn it. Better they don't use BTC at all! They surely will get robbed blind. 
Nobody is proposing a substitution to the metric system. What's being proposed is to simplify the usage of the metric system. Simplification is also tought at school, I think you missed the class.
It would have been a great idea. Except for the fact that the 21 million limit would have to change by the same amount of decimal places. It isn't going to happen. You can't willy nilly Bitcoin like the US Dollar has been.
And for all the anxious to get rich crowd. If Bitcoin does what it did last year it will be worth $52,0000 thousand each by 2015.
If I were going to buy pizza or beer I would probably use Bitcoin before ounces of gold. I would use Dollars first. That's why fiat like the US Dollar are here to stay. They are kept at a relatively stable price by the Federal Reserve.