There is no regulatory basis to reduce the 787's current ETOPS-180 certification as that allows for a flight to depart with an inoperative APU battery or APU.
So if regulators are going to assume that the APU battery is still likely to fail and inop the APU, that would still allow ETOPS-180.
What about the main battery failing?
AFAIK there is no MEL item for dispatch with a main battery inop.
