Marijuana prohibition--a modest proposal

I really hate politics, but if there is anything in the American political scene that would motivate me to get involved, it is the insanity of our drug laws.  I have a proposal that I would love to have criticized.  Tell me please why this would not make more sense than the current situation.
##
I have a proposal that would be far more fair, and would cut drug use by 50% in three years.  Promise.
It works like this:
1) Put together an evaluation system for measuring the danger/toxicity/addiction potential and/or any other standards of health and mental impact for drugs.  LD-50, addicts produced per thousand users, fatalities per thousand users, percentage of users that go on to other drugs, percentage of   users of drug "X" who began with drug "Y" (the "gateway" theory), etc., 
2)  Apply it to all psychoactive drugs  in the market, including alcohol and tobacco.
3) Any drug that gets a lower overall score than alcohol or tobacco (assuming a low score means less danger) is legalized.  Let's assume for argument's sake this is marijuana.
4)  The newly legalized drugs are sold only in plain generic wrapper, and taxed at a rate to make it approximately 10% cheaper than that sold by illegal street venders.
5)  The profits are all put into anti-drug campaigns and rehabilitation programs.
##
What would the results be?  Well,
1) the street drug trade collapses for Marijuana, and probably cocaine as well (not sure, but I believe that Nicotine takes the cake for addictive potential and fatalities, as well as gateway action).  As the street trade collapses, street gangs funding activities with drugs go bankrupt. 
2) The multibillion dollar drug cartels go bankrupt.  They can no longer afford the vast bribery that has kept them from prosecution.  Nor can they pay the armies that keep their rivals from killing them.  A feeding frenzy takes place, ending with greater stability in South America, the Asian Golden Triangle, and even sections of the Middle East.
3) Billions on nonviolent criminal incarceration is saved.
4) Billions in law enforcement can be shifted to violent crime.
5) Hundreds of thousands of otherwise innocent citizens are saved from jail, increasing overall social respect for law, and preventing the disruption of inner-city communities due to drug-related arrests.
6)  The vast sums poured into anti-drug programs would have a terrific effect.  What consumer product that cannot advertise could survive such an onslaught, backed by billions of dollars of research and airtime?
##
We could balance the budget in five years, I think, between the profit, and the reduction of expenditure, and the return to the workplace of otherwise harmless citizens.
##
And beside that, there are few things that irritate me more than Cocktail parties in support of "Just Say No" programs.  That has to be one of the most massive hypocrisies I have ever seen in my life.