So...what would happen if a drugslord or influential family would decide to make Supercoin his private coin and would start to accept it as a payment.

1.) He would start buying Super until it would reach an acceptable value.
2.) Make it known that he prefers payments in Super.

This would create a good demand so he can make profit on both sides and with the BTC reaching an "interesting value" this would create an enormous leverage, if you compare that to payments solely in BTC.