Just watched this episode with David L Jones, and the subject of a USB kill switch came up
We have done this before, you simply take both of the USB data lines to ground. This is the method of performing a "reset" to the USB device.
This can be done using a double pole switch/relay to mechanically switch both lines to ground, or of you want to control it from a logic level an open collector device like a 7407 / 7417 can be used to ground out the lines.
Have used this method for about 5 years on USB mice without problems, not tried it with USB 2 devices though as have had no need, so unless the extra circuitry interferes with the bus at higher speed, I don't see why it wouldn't work.