Pretty solid scenario ... He may not have hung around so long, so maybe no Norton,Shavers Holmes etc...
He may have benefitted from the 3½ years out of boxing. He matured mentally and changed his attetude. He may have gone lazy 1967 - 1970, tired of boxing and easy defences. Losing focus, getting fat and in the end retire after a couple of losses to of the strong contenders - Frazier, Bonavena or Querry.
Maybe....But more likely he lost his prime years, his attitude was fine in his prime, & he lost significant foot & less hand speed. Odds are he could have cleaned up in those 3 1/2 years.
He would definitely have cleaned up during that time. During his comeback he was at his best circa 1972-74. If his career had n't have been interupted,I reckon he'd still have been producing that form during those years. A small loss of leg speed would still have occurred.