even a hybrid drive has enormous potential fuel , cost and safety benifits
transmission losses.. remember the trend now for efficiency in jet engines is geared fans and these gear drives add weight, complexity, and consume power , electric motors are small, light (relative to a jet engine) and can be designed for any speed, torque relationship required .. the amount of gear creating wind-age is also reduced
motor size.. instead of fossil fueled engines designed to deliver TOGA power the hybrid engine needs only to deliver a bit more than cruise power, an insignificant amount of battery ( weight and volume wise) can supply TOGA (ludicrous amounts of, if required!) as well as power to land safely if main engine fails.
safety .. power from multiple fossil fueled engines can be (re)-routed to multiple drive motors so balance can be maintained in the event of an engine outage
cost.. the electric drives need a fraction of the maintenance and have far greater reliability . The generator engines can be modular and easier to swap (than a wing mounted engine/gear/fan assembly)