Hi, Ed
In your E-Stop setup, You can add a latching relay,(4 pol double throw relay) to Re-set the Gecko's and on E-Stop it Gnd's the Err/Rst pin's.
With your E-Stop in "Normal State", This Relay is wired to On/Closed, The Common Term's, One to each Gecko Err/Rst pin, NC's to Gnd and NO's to Blocking Diodes to a NO Push Button with 5 volt's on the other terminal, (Push & hold till the Drives Reset).
This allows all drives to be re-set only when in non E-Stop mode.
The 4th pol of the relay can be wired to Mach to E-stop Mach's Reset Button if the Maine E-Stop is Pushed
If you wire in an additional Relay (small 5 volt) contact's wired into this 4 pol Relays Coil, Mach can control the Drives re-set also.
With some Zener Diode's, Should be able to Halt Mach with a single drive faults also.
I've got a diag. around hear somewhere, Looking for It.
Hope this makes some sense, Chip