They could always film her through Vaseline and gauze, like Lucille Ball in "Mame." (of course, that was a wretched movie, in the end, too.)
However, I agree, she's too old - I also don't know that her style with a song would play as Rose - she tends to chew words and bend pitches quite a bit, and Rose is an in-your-face, bellow-it-at-you type.....I love to hear Streisand sing...in the right rep...just not sure this is it.
Upcoming: I'm about to be a busy, busy boy!
Musical Director - "Gypsy" at ATI
Vocal/Music Director - "Bloody, Bloody Andrew Jackson" at Phoenix