Interesting read. I enjoyed it.
Here's my take on the plug-in vehicle thing. I haven't done any calculations but the thought process is as follows:
In a conventional IC engine you take a fuel which has chemical energy and transform it into heat energy which you then transform into mechanical energy. Each of these steps involves a loss of energy which is quantified as efficiency.
In a plug-in vehicle you take a fuel and extract it's chemical energy to produce heat energy to produce mechanical energy to produce electricity which is transported through several step-down transformers to your house. You then convert that to chemical energy by charging a battery which is used to drive a motor thereby converting it to mechanical energy. Each of these steps also involves a loss of energy. One could infer that a greater number of energy changes would involve a greater loss of overall efficiency.
However, the scale of power generation (and the vast array of heat-recovery features in these plants) makes it quite efficient and the heat losses in an IC engine make it quite inefficient. Also, from the first post, the desire to have it all in one package (speed, comfort, safety, convenience) tends to reduce the efficiency of that package.
I don't know the answer but it's interesting to think about. I do think that if we eliminated all drive-up windows (my pet peeve) and built a feature into cars that minimized the time you could idle them it would save a bunch of fuel. And the bottom line is we are going to have to be better stewards of energy as the population grows and the planet does not.
Thoughts?

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".