If you want cheap missile truck, then Rapid Dragon, dropping missiles from cargo aircraft, is the answer.

The B-21 is the B-52 successor, and has to worry less about being shot down.

There are systems that are in bombers that Rapid Dragon does not deal with, and you need to expand the transport fleet that the Army and Navy and you also want for other missions. It's great for pounding fixed positions where you can load up and program on ground but not readjust in the air based on how it's going.

Also not all munitions work effectively with it. A dedicated bomber enables things like MOAB.