An opto-isolator would probably introduce more interference on the signal lines. You have to supply enough current to light an LED with an opto-isolator, as compared to triggering a high impedance input pin.
As for the other general "stuff happens" concern, I don't know that one can prevent the occasional miswiring in a cost effective manner. Even "professional electronics installers" occasionally miswire something or short something out. But if the thought of hooking up 4 wires causes you unusual distress then you should look into an obd based solution. What kind of car do you drive?
P.S.
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