I could see a few potential advantages to a hybrid system in this application.
VTOL operations are notoriously power hungry during takeoff and somewhat during landing, being able to use stored energy in batteries in addition to the generator output might mean being able to use a smaller engine.
I'm assuming the combustion engine in this case is a gas turbine of some kind, they tend to run most efficiently at constant speed and high load, systems that allow them a wider range of operating conditions tend to add weight, complexity and cost. At cruise the hybrid system might allow the turbine to run intermittently at high load to recharge the batteries, and shut down while the batteries drain. It might even be able to close off the turbines inlet/exhaust ports during shutdown to improve aerodynamics.
I see cabin noise benefits as well, at least during the time the turbine isn't running. Not having the turbine mechanically linked to any propulsion system might also have benefits here, as well as giving flexibility in where the turbine is placed. This could also improve aerodynamics and cabin noise.
Also they could implement regen, recovering some of the substantial energy used to get the aircraft aloft. Those lift fans look like they could do a hell of a job of that provided there's enough battery capacity to eat it.
The problem I see is that many of these concepts violate the principle of safety/redundancy as a priority in aircraft design. I guess there are ways to engineer redundancies into some of them. Multiple isolated battery packs, maybe even powered by multiple small turbines. I guess that's what experts are for
I'd be interested to see how it would handle total electrical failure, is there some kind of auto rotate type system that would rotate the fans vertical and provide a survivable vertical landing speed? One of those giant airplane sized parachutes?
Anyways, very interesting concept. Thanks for posting.