A big problem with keeping Sutcliff in the group, leaving aside for the moment his demise, is that my impression is that his heart never really was in music. I could be wrong, but I think Sutcliff saw himself as an artist, and his membership in the group was based on his friendship with John Lennon rather than any nascent musical ambitions. Therefore, I think he was always likely to depart the group at some point to pursue his actual artistic interests. Had he lived, he'd stay an artist, but an artist who happened to be close friends with John Lennon, which would probably be good for his career in 1964 or so, assuming Beatlemania hits on schedule. He probably designs an album cover or two, but not until the band moves into a period in which it wants its covers to be artistic statements, ie, late 1965-1966.