in these days is hard to make a change of the system of measurement of a nation. Just think about cars: all the new cars will mount a different tachometer (speed indicator) but this is the nothing: after this all the signposts should be changed, all the old cars should change the tachometer and the other instruments.
Industry and all the services will have to upgrade all the softwares to make machine works, and all of this without creating confusion (this data are inches, feet, meter or centimeters?).
Of course all of this costs money to the state and to private citizens...
etc.
It could become easily the Kaos.