I took the templating from the Oracle wording for Exalted Dragon. I'm trying to find other cards with attack payment requirements to make a more informed judgement.
[some time later]
I'm not really able to find any. I'm not sure, then, exactly how to template this card. Propaganda
used to have a wording similar to Exalted Dragon's, but now it and Ghostly Prison have the same Oracle text (the same as Ghostly Prison's printed text.) Exalted Dragon's Oracle text still corresponds to the "old way" of templating this effect. Since this card more resembles Exalted Dragon than it does Ghostly Prison, I'm going to leave it as-is for the moment.
Something else just occured to me. It appears as though this creature's drawback bears close resemblance to the drawback of
Goblin Prankster, also under development in the card creation forum. Should I change the drawback of mine or do they feel sufficiently different that they should be okay?