Wow, that makes complete sense. What an elegant hack!
The easiest approach is to just use a commonly available relay modules used with Arduino or similar platforms/microcontrollers, as they already contain minimum or all protection mechanisms. So, the module will contain the reversed diode in parallel with the relay, while additional transistor and optocoupler will allow you a complete galvanic isolation of the controlling- from the and relay circuit.
YouTube has plenty of user-friendly resources with schematics and functional overviews, just search for "relay module" or "relay arduino".
Great overview though, thank you for posting that.