“Small, highly efficient engine with electric boost for acceleration and hill climbs is rational. “
I’ve owned and driven countless vehicles and never have I said, “Gosh, I wish I had an electric booster.”
Electric systems are a waste of money, natural resources, contribute to pollution, and are unnecessary.
That's because you've been driving vehicles with engines that were much bigger than they needed to be. Necessarily tuned for a wide powerband which gives up a lot of efficiency, large friction losses, large pumping losses, all adding up to lousy gas mileage.