Nature doesn’t care about anything. It is not a conscious thing. The size of the Earth, however, is a natural phenomenon, just like the speed of light. It just isn’t a universal constant, relatively unchanging though it may be.

A multiplier is obviously going to be necessary whatever the base measure, because there’s no universal constant that happens to be of a useful, human scale. Or I guess you could use something like the wavelength of the hydrogen line – about 21.1 cm, a fairly useful length – but that isn’t really inherently a special wavelength, it just happens to be useful in radio astronomy.