Back around 1990, there was a PUNISHER movie adaptation that I liked better than the movie. As I recall, illustrated by Brent Anderson.
But yeah, bringing in war crimes conspiracy just convolutes and politicizes the Punisher's origin away from its basic appeal. Punisher is a character with a visceral appeal. Criminals killed his family. He's pissed off, and declares a one-man crusade to kill all criminals. At his best, Punisher is a more believable or "realistic" version of Batman. Why mess with such a basic formula?