For us city-dwellers, the start-stop system is significant. Even without the kinetic energy recovery feature of a hybrid drivetrain, the start-stop can potentially save a lot of gas if you spend so much time waiting at stop lights like I do on my commute. SO I think you're right - for city dwellers, even a very-mild hybrid should be significant.
We have 2 economy cars, one is a hybrid and one is not. In our 100% city driving routine, the hybrid literally doubles the fuel economy of our non-hybrid.
I believe a mild hybrid with start-stop technology could be very valuable if it doesn't add appreciable to cost. An alternator centric solution seems to be quite adequate for mild braking energy recovery and delivering that small amount of energy back for propulsion later.
Decoupling the belt/pulley system from the engine while it is stopped would allow the alternator/motor to keep systems like air conditioning alive. I'm sure the alternator/motor/belt/pulley system could be built robustly enough to start the engine.
The electrical storage system would need to be higher capacity and higher voltage. 48 volts might work.
I don't know all the reasons but it's looking like four cylinders with turbo charging is all one might need in the under 200 horse category. That can be pushed to 300. What does V6 buy you?
More cylinders seem to be required only if you must go appreciably more than two liters for an easy 200+ horses.
I can't really get too excited about this. It's not a compelling increase in efficiency, and from an engineering standpoint, it all just sounds like some kind of a band-aid afterthought. It's certainly not an elegant solution, so I'll just keep driving my environment-murdering gas hog until my flying electric car comes out.
All the automobile companies will be very much interested to use this technology in their top models.
They will expect that it enhances the over all engine power performance and the driving comfort with its higher efficiency.
That is certainly improved. No mention if this can displace the starter motor, or the increased battery-budget needed.
A starter motor pulling on the accessory drive belt does not sound like a recipe for reliability.