Gonna have to disagree with you on this one.
The advantage of decriminalization over legalization is that it is not growing the State's apparatus through the new payments it would get from legalization, such as licensing, taxation, etc. It's the exact problem that every proposal to legalize marijuana, such as Florida's Amendment 3 last year, has. Not to mention legalization gives immunity to corporations that sell the products.
I think the best solution ideally would be to write laws in a way that is intentionally vague to the point where drugs become alegal like with the Farm Bill.
Reputation is important for white, grey, and black markets, so I don't get why you're saying that reputation should be prioritized in white markets.
Also, how are grey and black markets not considered free markets?