I'm surprised that Garrison Keillor wasn't on
your list.  He'd be my top choice by far, for all
the right reasons:  fundamentally an amazingly
productive writer, tells lengthy, often complex
and surprising down-home stories based on his own
background, with more than enough humor, irony,
and  philosophical content to go around;  can be
a blistering social critic, and funny as hell.
Plus a musician and crusading, inventive radio
artist and comic dramatist.  I think Sam would
approve of him as the best candidate for
inheriting his legacy.

Ben