I am happy to announce I’ve just pushed the final part of the controller to the repo =)
The new device looks better than the MKIII one, you can mount it to any 10x20mm rail (the default option is to mount it onto the cyclic base one). With the new software, you can put the needed number of these thingies next to each other, using the standard short blue USB wires that come with Chinese Arduino clone boards and a USB hub.
Standard setup with a compact collective, equipped with a pedestal, requires one master controller, but for stuff like VRMax, you may need two of them.
Internally, its the same thing as MKIII but with an added MCU reset button (which was needed occasionally when there was something wrong with the firmware). The button is connected between RST and GND of the board.