Sorry, this is not an appropriate post for BDD. BDD is a harm reduction based forum for specific questions about drugs. We don't do "best" threads. We don't do legal discussion, laws vary so much from country to country, and if you're in the US most decent opioids are going to be covered by the Analog Act, which treats them the same as a controlled substance if the effects or chemical structure is substantially similar to a schedule I or II substance. We also don't do fantasy questions, or discussion of synthesizing drugs.
I can't think of anywhere to move this where it would be allowed. I suppose you could ask Drug Culture (or I can ask if you want me to) if it would fit there?
Please PM me if you have any questions.