Had George Lazenby stayed and done Diamonds are Forever and Beyond
He would be easily developed in all 4 dimensions as a serious pen-pushing, woman-bedding and cocky Englishman for a patriotic deadly assassin, akin to how Ian Fleming developed 007 in his original Bondverse, similar to how Pierce Brosnan and Daniel Craig would play the role in the Bondverse films years later and a HUGE far outcry from Sean Connery's Bond and his films' surrounding Swinging 60s influence that is eschewed to showcase harsh reality of living in a counterculture world like The IPCRESS File.
Now, Diamonds are Forever. 1971 - USA was hitting the box office with the likes of Dirty Harry, the French Connection, Straw Dogs - R-rated grindhouse psychological crime thriller B-movies with troubled yet hardened protagonists fighting back against inhuman cruelty in any shape, form and no good deed goes unpunished.
Had the film been directed by Peter Hunt and starring George Lazenby as James Bond, the film as On Her Majesty's Secret Service Part 2 yet a novel accurate R-rated psychological crime thriller with a troubled hardened MI6 agent out for vengeance. That film would make America (and Lazenby's native Australia where grindhouse B-movies were also big thing) earn an absolute killing. Broccoli and Saltzman would be gobsmacked at first then realise "We don't need Connery or Goldfinger after all. We just need to pay attention to the goddamn books! Ian ought be proud of this, Harry!"
Diamonds would earn over $210 million in worldwide box office and have minor criticism for its darker and yet slightly camp tone but praise universally for its performances, music, plot and story development and faithfulness to the source material.
Unlike Roger Moore, who wouldn't have got the job and brightened the film with his charm and humour, George Lazenby's Bond would have made Live and Let Die a more down-and-dirty grindhouse exploitation action film in odds with the other action B-movies of the 70s.
Lazenby would've done The Man with the Golden Gun, in which would have been more suited for him than it did for Moore, but would still have it's criticisms and he would then intend to end it on a high note with The Spy Who Loved Me, a film that would easily tie-in with the continuity of the Connery films and OHMSS/DAF. But, if Lazenby accepted the option to do an additional film to further fill his contractual needs - salary-wise and offers from other decent acting doors in future - he would have gone with more of a mega-big-bang high note by starring in a more novel-accurate and serious film adaptation of Moonraker.
Jaws would still be in it as he was in Spy, but imagine Lazenby's Bond in England for the whole story with the same cast from prior films, Hugo Drax would still be played by Michael Lonsdale but no outer space influence or Star Wars inspiration and Lazenby would not have been a fan of Bond going into space and Gala Brand would be the main Bond girl instead of Dr. Goodhead.
George could then end it there with For Your Eyes Only bringing in a new actor as Bond with potential canditidates like Lewis Collins, Michael Billington, Ian Olgivy and Timothy Dalton