Since the battery is one of the biggest expenses to replace when it no longer holds charge, the economics of it would be tricky. Nobody would want to swap their good battery that they've carefully looked after for one that holds much less charge. Not to say that it's not possible to solve, but it's not so straight forward.

Also, I've used lots of chargers greater than 100 kw, and they really don't take that long to charge a car. Combine it with a meal, even a fast food meal and they've generally charged more than I needed in that time anyway.

Fast charging is an outlier anyway. >90% of the time you slow charge at home for a third of the price per mile, and it's lovely to only need to visit a filling station on rare long drives.