This is interesting. I got no personal stake in legalization of pot, however I would like a unified and systematic scale to identify legality of drugs.

Something like: psychotropic index (hallucinations and stuff), overdose consequences, physical dependance, mental dependance, concentration/reflexes deterioration (basically how safe is it for driving, maybe establish limits like done with alcohol), long term physical effects, long term mental effects, etc...

This would allow a clear and consistent understanding of how exactly a particular drugs effects and legality of it.