In a hybrid cars, where the combustion engine provide power to the wheels of the car (and not only to the battery like in the old Volt from GM) gearing needs to be much more complex than in a car where the wheels only get their power from electric motors. In electric motors all you need is to reverse the plus and minus to the motors to get the car going reverse.
The idea of using an engine in the car to only charge the battery that drive the car is not too bad. Such a car could be both charged home (from those having a possibility for that) and while driving, using the engine in the car to charge the battery, making the range larger than the cars with only battery as fuel; an engine that is only charging a battery can be made to run in the most economical and environmentally friendly way as it needs not speed up or slow down. Also, the engine could be made to run on various fuel types. Maybe fuel cell or oil from fast food (have read about a car smelling like pommes frites out of the exhaust pipe) or other kind of fuel when available. Electric motors are not wasting as much energy as many other motors having few moving parts.
Not only thinking of cars for private use, but busses, trucks and cargo- and cruise ships; possibly even air planes.