There's always going to be a problem with impaired driving. If you create a different legislative scheme, it's not going to stop impaired driving.
Statistics and studies into decreasing rates of impaired driving have found that really the only mechanisms that consistently work are consistent, visible enforcement of whatever law is in place, and education of the public about the law and the fact that if you violate it you will get caught. It's that perception that has the most significant effect. It doesn't matter what the law is.
Changing the law is not going to solve impaired driving. Changing the law is not going to, in my view, make a difference. All it's going to do is create a different, unnecessary solution.