You're trying to re invent the wheel....C&H has an ignition with a rubber spark plug cap that uses the wire shielding screwed to the cylinder for a ground..NO ONE makes a screw on spark plug wire, they went out with the Model A Ford and 7/8 pipe thread spark plugs.. Only NGK makes a resistor spark plug with a removeable top. With the resistor wire used for the spark plug there's no way to screw it on...
What's wrong with the present system ?