Braking delta V depends on many variables such as mechanical condition, component temperature, road surface friction, etc and is thus difficult to predict to that level of precision. Even with real-time communications, if the vehicle in front slows less than expected due to hitting a pothole or something then the vehicles behind are going to have to react damn fast to avoid a collision. It might be achievable on certain roads but it will be a tremendous engineering challenge. Don't expect to see this in passenger vehicles any time soon.