I dont understand this part. The potential for overdose on alcohol is high as well. I can go buy a plastic handle for $10 and if i drink the whole thing tonight i'll probably die. I think the right path is full legalization similar to OTC medicine in the US. You have FDA verification you are actually taking what you think you're taking, no weird fentanyl substitutes or cuttings. You put warning labels on describing dosages and limits. You let people use them and get treatment if they abuse it. It's the same way we treat alcohol, just we are conditioned to think alcohol is somehow way more safe than something like heroin.
There are responsible drinkers and responsible heroin users out there. I know it may sound scary but I don't think there's a major inherent harm to having methamphetamine available over the counter. Some people will abuse it. Some people are already abusing it.