That would have been.... odd. He would have pulled off the solemn nature of Spock but I don't know if he would have been depth and odd charm. Landeau was known for cold, edgy characters. It remind me of Midnight Cowboy. They almost cast Michael Sarrazin in the role of the Joe Buck, Jon Voight's character. The person who cast the film literally put her entire career on the line and did everything she could to sabotage the production until she could get Voight from NY for a screen test. When you think of how groundbreaking that film was, who other than Voight could pull off the redneck "Aw, Shucks" male prostitute? You just can't see anybody else in that role. It's like that Nimoy for Spock.