So it is clear the end game is super capacitors for regeneration and acceleration and batteries for range. The capacitor should shield the battery by sourcing and sinking large bursts or current while the battery is charged or discharged at a slower rate. Every type of battery has its own issues with regard to charge rates / discharge rates and thermal properties. It would be great if we could decide on a standard power component interface. This would be a self contained unit with super capacitors and chemical batteries along with a microcontroller. This component would accept or dispatch power on command. It might communicate via CAN bus or some other protocol to get throttle. You also could sense speed to allow a full capacitor at rest and an empty one at speed to anticipate braking or acceleration.
Cheap powerful microprocessors change the rules with respect to economy of scale. It is now possible to have very sophisticated modeling controls for just a few dollars. So it makes sense to make it decentralised. integrating the capacitor and the chemical storage into one package, and providing a standard interface will allow multiple vendors. It would allow relatively painless upgrades and provide a platform for new applications.