With a good emergency broadcast channel you could get everyone around you involved in milliseconds. We should try to get the algorithms to work with local data only (and whatever info is in the emergency broadcast packet), and low-runtime algorithms. We might not be able to find the optimal soution but maybe we can find a solution that indeed minimizes accidents, inside that fraction of a second. Maybe just braking and steering away from the accident works in many scenarios? Because everyone steers away at the same time they leave room for each other without need for further coordination.
The fun thing about automated cars is that even the worst-case scenarios should be at most as dangerous as if only humans were involved. So we can only make it better. Everything is more ethical than letting humans decide in realtime imo.