Can a diesel-electric hybrid total weight be less than IC or jets? I don’t see how.
Any day NASA will announce the discovery of balloons powered by the hot air from Al Gore ,obama, and all the other champions of failed or narrow niche technologies.Technologies that just happen to make them rich through government subsidies are the politicians and advocates favorites!
I don't know.
I do "know", from talking to friends who are GA pilots, that there's some work going on in developing piston aircraft that used diesel, rather than spark ignition engines. This is driven by a desire to run them on JET-A, rather than AVGAS.
The diesel-electric setup would allow separating the diesel engine from the propeller nacelles ... possibly a good thing on a tiltrotor aircraft.