You list a number of potential increases in state power that would accompany legalization, but which of those do we not have already under our system of extensive criminalization of drug use?
Sure, maybe if drugs were legalized some revenuers would erroneously show up at my door looking to collect taxes for drugs I'm not actually producing. I'd have to go through the trouble of explaining that I don't produce drugs, and maybe let them look around my place to make sure.
But right now, I might also get a visit from the police based on erroneous information that I possess drugs. Only this time, it's not going to be a matter of answering a few questions and letting them poke around a bit. Under our current drug war, if the police show up at my place looking for drugs they are going to be knocking down doors, pointing guns in my face, and generally tearing my place apart.
Kids are already taken from homes because of drug use. Cops already enforce laws against public intoxication. How could the state get any more intrusive when it comes to drugs than it already is?
In the future, the feds will knock on your door to say it’s time for you to sacrifice your life to donate both kidneys because your federal medical records indicate that your liver will fail in 2-years due to drug use. If you die now, your kidneys will save two youngsters for years to come!
You underestimate the evil of big government.