I'm a little confused with this one. Was the APU not running? I'd have thought engines shut down, APU running, electric hydraulics pumps + PTU?
Another point mentioned was that this scenario might not have been considered when writing the QRH - I vaguely remember that the using the park brake as an emergency brake wasn't considered until an accident happened (can't remember the airline).
Differential braking should be more than enough to steer the aircraft even with the nose wheel scrubbing, how easy that is though is another point all together.....