Saying you want a third way is simply attempting to find a way to dress up moving away from prohibition as being a new and innovative policy. If there was a golden third way between prohibition and legalisation that prevents crime while allowing choice it would already have been found. While treating drugs as a public health issue may help reduce the number of people who are locked up for possession it does nothing to break drugs cartels or reduce the problem of supply so it is unlikely to be of much help to Mexico as the policy will mean reducing the help provided to Mexico while it is unlikely to have an effect on demand at least in the short to medium term. In short this would mean leaving the door open to the cartels.