There's presumably no more energy being dispersed than with manual brakes. The current brakes will heat less (due to energy in the ERS).
If the ERS is full, you either switch over to dumping the heat into the brakes (no ERS, switching problems), or you start to drain the ERS to make room (no switching problems). Draining the ERS will give you the same thermal problem you have with no ERS, except you have the choice of not dumping it into the brake pads - you can have seperate external resistor coils, glowing and radiating.
If the ERS is full, you either switch over to dumping the heat into the brakes (no ERS, switching problems), or you start to drain the ERS to make room (no switching problems). Draining the ERS will give you the same thermal problem you have with no ERS, except you have the choice of not dumping it into the brake pads - you can have seperate external resistor coils, glowing and radiating.