I know that the estop in the g540 is not a real estop. I would use a relay to switch of the 230V to my dc supply. It is not a good idea to switch off dc power with high current, unless you use a diode to protect things. And as Jeff says in some cases it would have to be a certified safety relay or other safety measures as mentioned in DS/EN ISO 13849-1. But this is just a hobby machine, so I don't bother.
The right way then is to press the estop and turn my steppers by hand if i get stuck at the limit switch
The relays I thing for the VFD I could try, but the inputs on my VFD is sink, and the 0v on the VFD and gecko have the same potential. I have not measured the current draw but i recond it is less than that of a small DC relay.
But okay it is worth a try
I don't want to switch a contacter for the VFD supply. I like it small and simple. I will live with the drawbacks then