What you are referring to is usually referred to as an EREV (Extended Range Electrical Vehicle). The reason legacy manufacturers market their less efficient plugin hybrid and non plugin hybrids (100% of the power comes from petrol) instead is because that's what they have and want to milk for as long as possible. In terms of drive train these are more complex to manufacture and more costly to maintain than an EREV. EREVs typically have slightly larger batteries than a typical PHEV as well. Typical electrical ranges are at least 80-100 miles or more in some cases. Usually the cars are available as without the range extender as well. This is less common for PHEVs and hybrids. Though of course some legacy manufacturers are still trying to push compromise cars. Like Nissan in this case.

Nissan has been really struggling for the last few years, this new hybrid engine doesn't look like it will turn things around for them to me.

EREVs are an idea that is not new and also relevant in shipping and aviation. Many modern large ships (oil tankers, cruise ships, etc.) are already EREVs effectively: an electrical motor drives the propeller and a generator powers the motor.

And there are are a few plane designs that are using small batteries + generators to power flight. It makes a lot of sense: electrical motors are a lot simpler, lighter and cheaper to maintain. Engine maintenance is very costly in aviation. And so is fuel. The recently announced X1 is a good example of a plane that does this. There are a few other manufacturers working on this as well. Early days but the potentially large fuel savings probably ensure this is going to happen one way or another.