[Garret]

Analogous to how batteries or a wall outlet supply power in an electrical circuit (power=voltage x current), motors only provide power into an mechanical system (power = torque x rotational speed). Since they use similar amounts of power you could use one to for slower speeds and one for faster speeds. All your doing is making a two speed shifter almost copying the effect of the AM Super Shifter or any other two speed transmission because all you are doing is changing the output speed but not the power. This isn't practical because you could just get a shifter and put both motors into it (compensating for different speeds of course) and get the same effect but double the power. Though you are correct that you could do it really just isn't practical.

About the Hybrids depending the type of drivetrain (parallel, series, or power-split) they may or may not necessarily switch between the motor and ICE (internal combustion engine). In a parallel hybrid the Motor and the ICE are simultaneously providing power to the drivetrain. In a series hybrid the motors provide all of the driving power and the ICE can act as a generator. The power-split hybrid is what you are talking about and yes they are more efficient than the others but only because the differences in energy consumption allows the motor to work for lower speeds (lowering power consumption) and the ICE and Motor to work at high speeds/loads (consuming more power) are so vast compared to the Fisher Price and CIM. This really results in having lower (than a conventional ICE car) torque at low speeds and higher torque at high speeds.