[chockablock]

Any reason they can't just route the current generated when battery is full to a big resistor/heatsink?

That would seem to avoid the problem of changing braking dynamics, and potentially save wear on friction brake components (pads, discs, etc)...

[frankus]

It's kind of a lot of power (hundreds of kilowatts for a panic stop from 60mph), so a reliable resistor bank would probably add more weight/bulk than it buys in reduced brake wear.

[nialo]

it's not really about the reduced brake wear so much as avoiding the sudden change in stopping distance when the battery stops charging.