In your deleted post, you said you had a simlink too etc, how did you solve the same issue? with the GPIO->reset pin? Also 3D printed case just something basic I threw together in blender, it needs a few tweaks. Total cost to have a fully stand alone Domoticz Linux server with Mysensors gateway = less than $30USD, what a time we live in!
Not sure what the deleted post said? Ill think about running an external disk, but not sure if it is warranted or not, have to look at how much this setup actually writes the disk, wear leveling etc etc, I have run lots of things from various flash media and not had a problem yet, touch wood! It would necessarily make this setup a fair bit physically bigger is the main thing I don't like.
Yeah, if there is no "offical" way of doing this, I will wire up a GPIO, it will also have the benefit of letting me flash hex updates to the gateway remotely, and if I ever need to, restart it.
So after finding Mysensors a while ago, I have actually sat down for a day, and got something working, almost..
I have set up an Orange Pi Zero with Domoticz, and have a Mysensors Serial Gateway connecting to it. I don't want the bulk size of going via USBserial, so I have conencted the Arduino Mini to the Orange Pi's UART port directly.
Domoticz seems to only let you choose a USB tty port, so I made a persistent simlink from /dev/ttyS1 to /dev/ttyUS20 and Domoticz connects to that OK.
The problem is, I assume, via USB Domoticz can restart the gateway, via serial it cannot, anyway, after a boot, until I manually hit the reset button on the Arduino, Domoticz does not actually connect to the gateway, and it will not list the version number etc, after reset everything works fine.
My first thought is to just edit the gateway code to have a delay before starting, to allow the Orange Pi to boot, but this is a bit hacky, wonder if there is a 'proper' way to solve this.
Here is how it looks with a quickly made up case 
I got to say, I love the size, and price of this setup!
I have a simple consumer whole house, single current clamp monitor. As I was looking into getting it to talk to Domoticz, I came across MySensors, this is great! So now I want to make a few battery powered MySensors to monitor various power loads, I have done a lot of reading, and want to make sure what I am thinking is correct before I order parts.
Because of where the sensors will be located, they must be battery powered. I plan to use the NodeMCU+NRF23L01 as a WIFI gateway, think this will plug and play with Domoticz, and this will be mains powered.
The sensors:
Arduino Pro Mini atmega328 3.3V - Modified remove power LED and regulator
NRF24L01+
100A SCT-013-000 CT Clamp
18650 Lithium Ion (one or maybe two in parallel depending on size, extremely cheap/free from old laptop batteries, 4.2v->Discharge->3.6v)
MCP1702 TO-92 regulator
Assumptions I am making, that I want to check before ordering parts: