Actually, IIRC, the coach at either Baylor or Boise, said they do exactly that. They recruit fast guys from the track team and teach them to be DB's. Although it doesn't seem to work to well trying to convert a WR.
I wish someone could explain to me the reasoning behind lining up 20 yds off the line of scrimmage and back pedaling at the snap? I do understand the concept of a single high safety, but...