Who Would You Cast in a Dick Cheney Biopic?

So Adam McKay, who directed The Big Short, is now directing a biopic on Dick Cheney. The cast follows:

Dick Cheney: Christian Bale
Lynne Cheney: Amy Adams
George W. Bush: Sam Rockwell
Don Rumsfeld: Steve Carell
Colin Powell: Tyler Perry (!)
Nelson Rockefeller (???): Bill Pullman

Now, I am not a modern casting director. But this looks absolutely insane. Was there not room to cast Christopher Walken as Kissinger? Or the decaying corpse of Harry Dean Stanton as Gerald Ford? I need to see this just to see what the heck is going on here.