I use a Pilz safety relay which sends an e-mail stop signal to the motion controller, takes power off the driver power supply, and also removes the enable signal from the drivers. One of those should stop the machine! The safety relay is tripped by the e-stop switches and the driver fault signals which are all wired in series. There are enough relay contacts on the safety relay to do that so, as you say, for the sake of a piece of wire it's easy enough to do. I wanted to make sure that the stall detect would stop the machine as I am using slaved motors for the X axis.