Raspberry Pi as MODBUS HMI panel (RPi-as-HMI)

I need the HMI (an operator panel) for a device communicating as a MODBUS Slave. I used the panels of SH-300 class and I want to create a prototype for the new generation, based on the touchscreen monitors.
Basically, the system consists of 2 parts, placed at the distance from hand-reach to 100-200 meters:

I'm going to use Raspberry Pi Zero, but I want to be able to use the RPi 3 with the HDMI display the mouse-keyboard at the development stage. 
The preliminary experiments show a good chance of success. Now I'm in the state of developing the software for Raspi and adapting the firmware of the Slave. And, since my "tries and exceptions" have consumed a lot of time and efforts, I want to note my steps for the future use.