You can already grow your own.Some interesting ideas. But never underestimate the tendency of the really stupid to inflict self-harm. I suspect that the only thing that would really reduce tobacco use would be to have a situation in which all tobacco companies are banned and smokers are forced to grow their own. The problem with that, however, would be that it would lead to an immediate underground market.
15kg a year.
P.S. there already is an underground tobacco market.