Read the report itself at DOTARS website.
The plan is reasonable but the devil is going to be in the detail as usual.
I think at present we have the "eight hour" rule. However since BAC decreases at about .01 per hour, it is concievable that a night out could leave you with a non-zero reading when you turn up at the airport.
Why is this important? Because you can bet that the politicians will demand a zero level with zero tolerance.
The other issue is Cannabis. This has a half life in the body of seven days. I don't use the stuff (and neither should you), but I wonder if being in the same room as a Cannabis smoker could produce detectable traces? I suspect that this issue is going to be settled in Victorian courts.
As for amphetamines, etc. they metabolise quickly so if they are detected it is a sure bet that you have deliberately done something wrong.