E2, I admire your love of language.
One 'BUT' - wouldn't your example be a normal advocat?
Gainsayer:
That's not gonna work.
Advocate:
But have you considered X, it offers most of the features you said are important with your idea Y, but it doesn't have drawbacks A, B, and C, and it's also cheaper.
Devi's Advocate (having no idea about a product taking Gainsayer's site for sake of argument against Advocate):
We said it is not gonna work, not with X not with other features, nowhere, no way, NEVER! And let's wrap it up, you are ridiculous in your pitifull attempt to win this argument. (No facts, but attitude!!!)
It is the way I see it - I could be wrong.;