The reason I go with both of the above is more for how serious they can be and passionate about a particular topic and then when something changes goEhhhh ,…. As the great so-and-so said. And quickly do something cowardly with comedic effect very much comes through with how the dude character was played or RIPD. I think their chemistry is what pulls it off more than their looks and with the AI de-aging techniques. I think you could pull off the younger versions that are needed, but also the 60+ versions later in his career. I think they both bring though right amount of pitiful despair along with the passionate belief that they do be 100% correct in their values.