The Circuit that I have uploaded at least needs 6 wires, (2 for IGnition Kill, 2 for Ignition start, 2 from Gen 12V+-) rest 2 are from Battery +- which are already in ignition start and kill wires; so no need to separately bring wires from battery if you can figure out battery + and - from ignition start and kill wires.
That diagram was for those having very little knowledge and equipment and you need a multimeter to figure out battery + and - wires from ignition switch wires.
Which 4 wires are you using for simple on-off system?