Morphine and codeine is a result of separation of opium; heroin a result of transformation of morphine.
As a quasi libertarian on the issue, I do not partake of any current street drug myself and would be unlikely to under looser regulations, but would like to see the issue medicalized (in a non-Bummercare, private system) along with other drugs that the FDA deems too risky to mainstream like the new female Flibbertygibbet or whatever it was called. If certain physicians establish a bond or insurance bloc such that they can be financially responsible for any permanent ill effect of the drug, then those physicians can prescribe anything but suicide medications and pharmacies can lawfully provide it.
I personally would support a Prop 19 for all plants.
I would support what you suggest, or something similar, for cocaine or heroin.
I’m not sure about cocaine or heroin being sold in convenience stores.