You know how they could have saved George Reeves' career?
He had starred as Superman on TV. But that ruined him. When he appeared in a movie around that time, members of the test audience saw him and started murmuring, "Superman! It's Superman!" His part was trimmed down to nothing.
Here's the way out of the typecasting. They should have put him in a movie where he'd go through the whole thing with his leg in a cast and he could constantly hurt himself. Maybe have him appear in a gun battle. When the other guy runs out of bullets, he could throw the gun at Reeves, hit him in the head and knock him down.
"OW! OWWWWW! My head! My head! Owwwwww!" Reeves could have said.
The audience would forget all about him having been Superman.
Other actors have done things sort of like that.
After playing Moses and Ben Hur, Charelton Heston played a swingin' architect in Earthquake and an equally swingin' pilot in Airport '75.
Steve McQueen's wife did most of the driving in The Getaway, and his character had very poor driving skills in The Hunter.
So here's what Mel Gibson should do. He should do a sequel to his old Australian movie, Tim. He had played a developmentally disabled 18-year-old gardener who marries his middle-aged employer. In the sequel, Tim could be a widower. Lonely and depressed, he innocently joins a neo-Nazi group, but soon realizes his mistake and quits in disgust.