One major problem of battery systems with electric vehicles is the efficiency on stop go - discharge-charge(regeneration) cycles.
The battery system is designed for less leakage and high capacity.
Even if its possible to have high discharge currents - the overall efficiency on electric breaking with regeneration and recharging the battery is poor and /or wears out the batteries.
This is why I think that a concept with a 2-way battery system might be interesting.
The storage system is optimized for no leakage and high capacity - but less peak current -
which is connected to a second system optimized for peak currents, with less storage and high leakage but almost no wear-out.
Stop and Go would be operated by the peak current system - if you are on speed - the energy would come from the storage system.
If you start the car - the peak-current system gets charged by the storage system - and here we go.
For stop-go you need a storage capacity of maybe 50-200Wh - not that much. It should be possible to make an optimized electrochemical or whatever system that fits this needs.
What do you think ?