[El Gato]

Wing spars on a low-wing airframe are in the wrong location -- bombs have to fall through them.

Looking at the picture of that airplane, it appears there's plenty of room forward and aft of the wing box for bomb/missile bays. Put fuel or avionics in the wing box. I think it would make a good bomb truck. Of course the Air Force can't afford to re-engine the B-52, so no way could they afford a militarized version of a 777.

[Paleo Conservative]

Looking at the picture of that airplane, it appears there's plenty of room forward and aft of the wing box for bomb/missile bays.

Considering the center of gravity of the plane is over the wings, putting the bombs fore and aft of the wings would cause problems with abrupt changes of center of gravity when bombs are released.