I'm surprised that you are jumping for joy at the prospect of getting rid of this "Ace" for prospect/s at the same time you make the case that he's a proven, affordable, legitimate front of the rotation guy. It is rather unusual to trade such commodity in baseball. Specially when they're affordable! What gives?
If your answer is, well, he is a late blooming, unconventional knuckleballer who is 38 years old. And I would never trade Niese, Harvey or Wheeler if they had such year as Dickey for prospects. Well then, is it possible other teams are thinking just like you?