Interesting and highly plausible scenario ExSp33db1rd.
Just to be clear, your thinking would be that the trim had run all the way forward, the crew were holding full backstick, THEN realised they need to used the stab trim cutout switches? In your scenario the aircraft would now have full nose down trim and no electric pitch trim. Their only option left was the manual pitch trim, but you can't wind that quickly enough to recover with a high rate of descent from 5000'.
Have I got your thinking correct based on the previous incident?