In 2,500hrs of operating the B200, I not once took off with approach flap, unless I was clearly in need of it (obstacle clearance take off).
If you suffered a donk failure, you're going to want to clear those obstacles, not reduce your ground roll on a runway where you're already only using like 1/3 of the runway.
A colleague I was talking to one day who operated the King Air and used approach flap for take off, went to Flight Safety for a course on the King Air. They showed him the climb penalty for taking off with approach flap. Needless to say, he never took off with approach flap again!
morno