Why not a diesel/electric. The diesel powered alternator only starts at the request of the battery monitor and then runs at it's most efficient RPM. The driver would have no control over this charging unit. The car is driven by inboard mounted wheel motors. ( flick a switch for 4 wheel drive )
but all 4 will regenerate when your foot comes completely off the throttle pedal. The wheel motor concept eliminates the expensive differential gear sets.
This would be a good tapering off vehicle. You got your diesel (to keep us happy) and an electric car to keep the environmentalists happy.
The little three banger in the Smart car will turn one hell of an alternator.
Comments please.

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom