The Cessna Skymaster famously had the capability to fly in the flight levels on the rear engine alone, and far greater distances than would have been possible with both engines running. One engine at max continuous is much more efficient then two, each at half that power.
With a relatively modest lithium battery pack, charged on the ground with solar or wind energy, taxi to departure could be done on electric, then start and runup on the ICE rear engine for the departure and augmented climb to cruise altitude in less tan 15 minutes. There, the electric could be shut down, remaining battery saved for emergency use. Cruise at altitude is much more efficient than at near sea level.
Returning to the lower altitudes, the pilot could determine how much of the remaining solar/wind energy he should use before landing, thus reducing the carbon use to the extent that safety was not reduced.
Battery capacity for 15 minutes at 150 HP equivalent would meet these requirements, and a significant reduction of the gasoline tankage to correct for the lower fuel burn climbing and cruising up high, and the weight penalty would be more modest than assumed here. This plane doubtless cannot go 800 plus NM at 10,000 feet and 125 Knots, but may do near that.
Power out approaches to airports often fall just a little short of the runway due to miss judging the energy remaining in altitude and speed, with this plane, even 5 minutes of cruise power in the airport vicinity would make a huge difference in the last minutes of flight.
This seems to be a hybrid that can work, as opposed to a primarily electric airplane. This should reduce fossil fuel burn by at least 20% on most flights, and more on shorter flights. The passenger/cargo capacity should still be quite good. Most GA flights have only 2 people on board, so typical travel would not be constrained.
Those of you who have made a GA business or pleasure flight with more than 2 persons on board this year, chime in and tell us how many of your flights did have more than 2 adults, and how many had 2 or one.
The train system within the Netherlands is quite fast and convenient, but the trip to England, Spain, Portugal or Italy is via Paris. The Scandinavian countries are not easy to reach. All of these are an easy flight in a Cessna Skymaster.
