Maybe 25 years from now, when Arthur is 117, he'll direct a revival of Billy Elliot and he can have Joey McNeely re-choreograph it for 3 boys who can sing and act but not dance. Humorous, yes, but not really a valid comparison. The plot of Billy Elliot requires that the character be a great dancer. There's nothing in West Side Story that says Anita has to be the best dancer onstage. Traditionally, she has been because that was the original director's intention, but whether it's Arthur Laurents now or someone in 50 years, there's nothing except tradition to bind them to that standard.
If someone can find an original script that includes the line "Gee Anita, you're the best dancer and you look so pretty in your Americanized bobbed hair and lavender dress," by all means, have at it. But it's not a part of the show. In 50 years from now, no one who saw the original direction will be around anymore to expect these traditions to be maintained. Maybe then West Side Story can actually be revived, in the truest sense of the word, instead of just copied.
Like a firework unexploded
Wanting life but never
knowing how