Just looking at this D,
 
Dont quite get it.
 
So the big bulbous thing bolted next to the engine with the battery cable running to it. Is that an induction motor that produces charge/ battery power from the motor - a battery charger?
 
Or does that take power from the batteries and provide drive to the motor crank via the serpentine belt?

hmmm. Interesting concept. So its a DC motor hooked to some batteries with a fancy electroncs board to make sure the current goes in the right directions at the right times. Simple ideas can make the best ones.
 
you would be limited to the amount of torque that it can supply based on the what the belt can handle.
 
As long as it works as a helper, and not to replace the engine, I could see that it could provide some benefit, but it  would be good to see some actual test numbers.
 
It sounds good in principle, however, as it has to go through belts and the crank bla bla blah, you would lose a heap of effenciency. Like you said, the closer to the diff the better.
 
It also seems like it would be a sizeable input cost. If you install that in order to gain savings and therefore pay for itself, I think you might be disappointed.