Helicopter friend used to race cars and had researched using large capacitors for short burst energy both racing and in CatA, your concept updated to new battery tech is the same principle. We already “store” excess energy in rotor spin, and increase rpm to store more. Makes me wonder about my misspent youth wrastling A models off a hot deck by beeping the rpm down to 97 and matching N1’s. No CatA in those days, reject was into the water until you hit 35 knots.
We build to match a statistical outcome, and there’s always new tech down the pipe, whether this electric, or new FADEC with 5,10,30 second power scaling tied to profile accuracy from Bell 525 type FBW.
Here's more, including the F1 racing slant.
https://en.wikipedia.org/wiki/Kineti...ecovery_system