I would actually kill for this... I spend half my time working out of the US and having to carry an extra convertor got annoying.. I finally just resorted to buying a couple chargers when I was in Europe.
I find it strange that it wouldn't be cheaper to make one worldwide model with different plugs, but who knows..
I've thought about tearing one apart to see how big of a pain it would be to make my own universal power supply, but I haven't gotten around to it yet..