I wonder if there are Godelian consequences of this. Such as, "I name the card Blankety-Blah, which we have decided is a Treasure worth $6 that you gain if and only if you ever name this card due to a Contraband."
At first glance I don't see this "problems", as you can only name a card and not define what it does. So you must have defined this card before, and than you basically have a house-rule for an additional card "Blankety-Blah" and of course for "Contraband".
But interesting question...
Edit: Thought a bit more about it. Still no. Because: If you assume that there is any card out there that you can bring into "existence" by naming it or interacting with contraband, you assume that there are more cards out there than the ones officially designed. If this is the case, there is no reason why you don't can't assume any card you like to exists, including the "Card of extremly overpowered counterexample" which says "You win! - If you think of this card, it will appear in your hand."
So basically - to exclude this counterexamples - you have to restrict yourself to cards that already exists, and so you also can't generate a "Blankety-Blah" with a Contraband. Because then you also would be able to generate any other card by any other non-restricted action. Like thinking.