Here's the list of broad topics issued by Schieffer:
What's missing? Big stuff.America’s role in the worldOur longest war — Afghanistan and PakistanRed lines — Israel and IranThe changing Middle East and the new face of terrorism — IThe changing Middle East and the new face of terrorism — IIThe rise of China and tomorrow’s world
No questions on the Pentagon or defense spending -- a clear point of difference between the candidates.
No questions on the criteria for the use of force, whether in Iran or Syria or ... Mexico.
No questions on the war powers of the President, either regarding Iran or drones or targeted killings.
No questions on [my favorite topic of] civil-military relations.
Maybe Schieffer will shoehorn some of these issues into his announced topics, or maybe the candidates will broaden their answers. I hope so. Otherwise, this will be a truncated and woefully inadequate one.