[Phantom]

Have you considered adding an injector kill switch? If you did that you could warm the engine then cut the injectors at a stop or roll as you do this open the throttle 100% and use the electric motor to turn the engine and trans for city driving. That would reduce pumping loss and should keep the electronics on in the car, the one thing you will need to remember is to let off the throttle and shift into neutral when you are ready to restart the engine.