Alright, what about the Electro-Motive Diesel engine (EMD), or ‘pancake diesel’
https://en.wikipedia.org/wiki/Electro-Motive_Diesel#EMD_‘pancake’_diesels
These lightweight radial engines were used to generate electric power onboard submarines, so that they could be propelled electrically. Could these likewise be useful for generating electric power for an ePPG?
What are the pro’s and cons of that approach?