You could use an SSR but TBH, they can be a bit expensive. If you decide to go that route, make sure you buy a DC one, not an AC one. If you try to switch a DC load with an AC SSR, it will go on but you won't be able to turn it off. CPC have a very limited range but Farnell and RS have a lot more to choose from.

That schematic shows all of the axis drives passing through the relay. That would make it a BIG relay and switching DC is more tricky for the contacts than switching AC. If you go this route, you'll be needing a big clonker of a relay, possibly more of a contactor and make sure it's actually rated for the DC current and voltage you would switching in a fault condition. I haven't gone that route myself. I use the drive enable signal into the drivers to inhibit them if I need to use the e-stop or the controller / VFD get upset. If the worst comes to the worst, I could always kill the mains using the front panel isolator. Certainly, if you switch the high power DC loads, you probably won't want to be using an SSR unless your bank account is very healthy.

I have SSRs for the flood and air (300VAC type) and for the spindle gear solenoids (60VDC). My mains is switched with a front panel isolator and I have a time delay relay after that to soft start the 100VAC transformer / diode bridge / electrolytic circuit. The e-stop kills the drives and the Acorn and the VFD via the low voltage inhibit circuit. As I said, if that were to fail I'd kill the mains. This isn't an industrial safety critical system, just like the other systems here, so there's no point kidding yourself that there is one approach you must take.

If you go the route I went, there's no need for heavy relays in the power circuit. If not there are probably contactors out there that are in common usage for this kind of application that somebody here could recommend.