My picks:
Jock: George W. Bush (who else?). If the Hollyweirdos can pretend to be pols, GWB can pretend to be an actor.
Miss Ellie: Sissy Spacek
Cliff Barnes: George Looney (perpetual loser)
J.R.: Tommy Lee Jones (a meaner bad guy than Travolta)
Sue Ellen: Delta Burke
J.R.'s mistress: Anna Nicole Smith
Bobby: Luke Wilson
Pam: Rachel McAdams or Emmy Rossum
Lucy: Paris Hilton
Jerry Stiller as Digger Barnes.
Ooh, your version would be a lot more fun to watch than the one they're proposing. LOL.
Cliff Barnes: Billy Bob Thornton