Ever since Streisand was cast in the movie, the myth of the desirability of a "Younger Dolly" has been much overplayed. Yes, Dolly Gallagher was younger than Ephraim Levi when they were married, but she is no longer.
More to the point, the play depends on contrasts (and similarities) between the romantic desires of the younger characters (Irene, Minnie Fay, Barnaby, Cornelius, Ermengarde and Ambrose) and the older ones: Horace and Dolly.
The idea of an older widower wishing to marry a young girl was a staple of stage comedies going back to the commedia dell'arte. Just seeing an older man wishing to wed a young woman created an instant comic tension ("Oh, no! She should marry that nice young man who loves her!") that always led to a happy resolution.
It's the same young lovers/old lovers dynamic that can be seen in A Little Night Music...and hundreds of other romantic-comedy plots. But one group of lovers has to be YOUNGER and one has to be OLDER.
So if Dolly is young or sexy, the point is lost. Why should Horace want Ernestina over a Younger Dolly?
This was true going back to The Matchmaker, which starred the 59-year-old Ruth Gordon on Broadway and the 57-year-old Shirley Booth in the movie, and The Merchant of Yonkers, which starred the 55-year-old Jane Cowl. (Those ages were all reported as younger in a similar thread here a few months ago, but I just checked them.)
One has only to watch the amazing Pearly Bailey do the speech to Ephraim before "Before the Parade Passes By" to understand that the character of Dolly MUST be a middle-aged woman asking for a second-chance at happiness before she becomes an older woman.
And as for Patti being too brash, that's just silly. Horace refers to her as a "damned exasperating woman." They almost called the musical that.
There isn't an actress on Broadway woman more exasperating than Patti LuPone.
