I have breadboarded a new control setup and am now about to build the panel.
It uses the USB interface and appears as an HID game controller.
It has slider controls for port and starboard throttles, steering and bowthruster. These work on the absolute position of the slider.
It also has buttons for throttle up, throttle down, throttle centre and wheel to port, to starboard and centre.
Further buttons provide horn, chart zoom in & out, tie up, cast off, next/previous WP/vessel, Show/hide chart, show/hide objectives, hide all controls.
I can create additional buttons and assign them to any keystrokes.
In the settings I have had to select the Saitek AV8R-01, as this seems to be the only one that recognises the full set of controls. Unfortunately it does not seem to distinguish between bow and stern thrusters - it operates the two together (on the cruiseliner at least).
Unfortunately I have not been able to find any documentation on how shipsim uses the HID game controller, so it has all been trial and error.
Anyway, I have all the above working and now it is time to build the sliders and buttons into a panel. When I have that finished I will post a picture.