Joules actually are Newton-metres, in a sense. A joule is (genuinely) defined as the work done when a 1 Newton force displaces a mass by one metre. So as long as you're willing to risk the Bureau international des poids et mesures assassinating you for your physics crimes, you can totally pretend that Newton-metres are for measuring energy and Nm/s is a reasonable way to measure power. While you're at it, you should measure torque in Coulomb-volts for the same reason