As to the OP's idea of adding an electric motor to the engine...
The belt is made to drive alternators, power steering, and A/C compressor. I don't think it would handle much power. I don't think this would be a very efficient way to add power. In fact I would suspect that the added weight, would diminish any advantage to less efficiency overall. I don't know this but I suspect that it would be kinda like a hydrogen car. Don't they have much less efficiency? Hydrogen is not free, it takes more energy to make it for driving than it does to drive with gasoline.
I think the pusher trailer is likely to be more efficient. Ideally a electric motor between the engine and transmission like the GM Hybrids would be ideal.
Later,
Allan Greenblazer
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