Alright, I dig that. That would be very plausible, and lead to a definite decline in Outcast power as well as create a scenario much akin to the methadone/heroin situation a lot of western countries experiment with atm - however there are a lot of moral issues for governments to deal with when it comes to substitutes.
EDIT: However there are a lot of drawbacks to using substitutes too. Here in my country there's been a lot of trouble with people getting more addicted to the substitute (methadone) than they ever were to the primary drug (heroin), so the most positive results have actually come from state-ordained drugs (heroin in this case). That might be a more viable solution in the Disco-verse too: State-ordained Cardamine.