Remove Halle Berry and keep Rosamund Pike as the only Bond girl
Instead of making her a villain and having Halle Berry as Bond's love interest, imagine what the film would have been like if you completely removed Berry. Instead the only love interest is Pike who instead of just turning out to be a double crosser at end, she has second thoughts after Bond convinces her he is mad or something and turns out Graves is the one who kills her after she confronts him on the plane about his world plans. Imagine then the fight scene between Bond and Graves with Bond being able to turn her to his side only to then lose her. Makes the finale the more dramatic when it's only him in the crashing helicopter getting out alive. Instead of his other 3 films having a happy end, here it ends with him as a lonewolf.
Of course the studio wanted this to be very light hearted yet that is how I would have made it.