I get the anti-prohibition deal, congrats to you.  On a cerebral level, I get it.  In practice, I believe smokers have more battles ahead.

I have some serious questions.   If pot is to be treated like alcohol, how do employers prevent users from coming to work under the influence? We all know that THC is stored in the body for quite some time.  Alcohol flushes quickly.  I would suggest that pot smoked the night before is still active in ones system  12 hours later.  

If I was an employer, I would be hard pressed not to maintain zero tolerance.  It's hard enough not to have people at work drunk or hung over without having to deal with stoned/ half stoned individuals.
I would argue that employers should / will have to bear the burden of  1. Setting THC levels  2. Incur the cost of testing.
I would presume employment and random drug screening would have to increase at the employers expense.