Saint: Don't think that is possible, because there will always be constants. You could somehow change the gravity of earth to be 10 instead of 9.8 but that wouldn't make gravity on the moon fit any better. You could use celsius (actually, the metric system uses kelvin) instead of fahrenheit and make things "fit" with water, but things still doesn't fit for melted iron. So there can't be a perfect system.Besides from those constants, I think the metric system comes close, except for the fact that ideally one litre should have been 1 m^3 instead of 1 dm^3, and one gram should have been what is now known as a ton.
The litre->kilo conversion and the temperature scale works with water in the metric system, which is not perfect but it's just as good as picking anything wierd as nothing will work on everything...
Anyway, I think americans use a good half of the metric system (well, actually the SI system), like watt, volt, joule, second etc. These all convert good to metre and kilograms. Why americans don't have a seperate joule based on feets and ounces instead I don't know but I'm thankful for it.
