Oh, easily the role he was offered of Ben Rumson in "Paint Your Wagon". Isn't it as easy as falling off a log to imagine him ruggedly singing "Wandrin' Star" and giving a superb acting performance? A super musical with intelligent and pitch-perfect western-friendly songs with lush orchestrations and chorus work, all worthy of his talents.
It's such a shame Disney didn't employ him in one of their live action films of the 1960's or 1970's. Bing was admiring of the studio for whom he'd worked in the 1940's. As with many of his generation, he was very much against what he perceived as the permissiveness of the then modern day cinema but cited Disney as an exception for whom he'd again work. I could easily imagine him as the singing scoutmaster in "Follow Me Boys" or as the less demanding part of the grandfather in the later, "No Deposit, No Return".
Part of me, for quality control reasons is relieved that he never succumbed to any of those Airporty, Earthquaky, Swarmy all star disaster films of the 1970's but I could easily imagine him trying to keep everyone calm in "The Towering Inferno" - sharing the screen with Fred one last time.
Plus, as a straight role, I felt it was such a shame he didn't play a lawyer in a courtroom drama. I think he had the acting authority to have easily coped with facing down unreliable witnesses or appealing to the judge and jury. Watching him fulfil his also refused title roll in Columbo would have been fascinating.