i worked on something similar in the mid 90s.
plus if you read about what happened post the uk kegworth crash, there was quite a bit of research into whether tail cams should become regulatory. they didn't.
e.g.
http://www.flightglobal.com/FlightPD...20-%203298.PDF
tech has moved on since then, and costs & weights have shrunk. low cost forward vision systems are a reality already, no?