I don't think I overlooked anything you said, in fact I totally agree with the "marriage in heaven" for EVs comment. What you didn't point out was the high self discharge rate for supercaps which makes them a bad choice for medium or long term storage and that is why I added my comment. As well as reducing the number of cycles for an EV battery a supercap can reduce the maximum charge and discharge currents the EV battery is subjected to during braking and accelerating which will also prolong its effective life.
