It works yes, good to prove a point and get things rolling. A long lasting successful design will need to be optimised for the technology, therefore offering much better efficiency and operating costs. Using the technology to its full extent means you can save a lot of weight and offer better performance over the present machines.
If you look at cars simply retrofitting a petrol design works, but it is increased weight and poor weight distribution. A purpose built car with in hub motors, batteries set low along the chassis and low weight structure that does not have to carry the forces of engine torque and transmission makes fro a much more efficient vehicle. Hence when you weigh up hybrids, the technology is eco consumer appealing but doesn't achieve much in actual cost savings.
Dash-7 is a 40+ seat aircraft, and limited airframes remaining. Not really sure it would make a great test bed, to carry the two outer heavy turbine engines and accessories the wing structure has to be heavier, wasting weight on structure that's not required.
BTW engine efficiency for electric is very different to turbine or petrol. So switching off engines in flight is not really any better than keeping them running at low power/drain, it's probably worse, as the dormant engine will just create drag.