That's probably not going to be effective. Look at devices with cheap universal motors and the like. They spew out tons of noise and a lot of them have a filter

That's probably not going to be effective. Look at devices with cheap universal motors and the like. They spew out tons of noise and a lot of them have a filter on the input to cut down on noise but as far as decreasing wasted power, the RF noise is a tiny drop in the bucket compared to the total power of whatever power tool or vacuum we're talking about. Also, the filter that they put on the input to try to combat this doesn't increase the efficiency of the device. If anything, I'd be afraid that there would be design changes to decrease the thermal losses of a device even if it increased the noise it put out.