He would really only be serviceable as a long man. Would he be any different from he is as a SP, as a reliever? It's not like his knuckleball would "play up" out of the bullpen. And it would be hard to bring him in with runners on due to the passed balls.
Might be able to get value out of the dickey effect if you brought him in to pitch one time through the order and then put the real SP in.