An interesting concept. Shame you didn't tell us anything about the power unit itself. I presume it's a starter/generator replacement for the alternator, as hub motors, a new axle or a sandwich motor would have to be bespoke to the car.
A new starter/generator will surely create a few (probably very costly to overcome) obstacles regarding the strength of mountings/pulleys etc, let alone the difficulties of making a one-size-fits -all system control unit which results in smooth and efficient progress.
The part you've described, the battery pack and charger, is surely the easiest part of any system to engineer. Anyone with an ounce of electronics knowledge could knock one up in a garage using a pile of shop-bought Lithium iron batteries and a switch mode power supply. Come on Autocar, get a decent reporter in there.
