I guess I first heard of Sharon Stone in 1984, when she was one of the large ensemble cast of the shortlived TV series "Bay City Blues" (and the only one whose career seemed to vanish as soon as the series did -- my usual brilliant success as a predictor!
Kelly is definitely a blonde for me too (unusual for me when visualizing fictional women, for some reason). I pictured her as the cool, rather classy type of standard-TV-blonde -- perhaps like Shelley Hack when she was on "Charlie's Angels" -- rather than an obvious sexpot type like Loni Anderson or Suzanne Sommers. Or from today's TV, maybe Kelli Williams of "The Practice." Someone who suggests that she might have more resources in reserve than she's showing at present (I'm not committing myself as to whether this is true in those cases, mind you).
I like the idea of Frances McDormand as Marion. It's hard to think of someoen who's reached name status without conventional attractiveness, but I think she has. Laurie Metcalf might be another (and she's played a cop too).
I'm glad to see "the casting game" revived. I wasn't able to get anyone to play with me last time I proposed it!