Regarding Follies: I'd love to see the National Theatre production transfer to the Beaumont, with a cast of Broadway legends.
Regarding Evening Primrose: From what I understand, CBS (?) still owns the rights to it. There have been a couple of concert versions of it, but even those were put on with some very special permission, or some other restrictive circumstance like that. Would love to see another, or even to see someone attempt to stage and adapt it, but it seems like the powers that be don't want that to happen, for whatever reason. Or maybe they just don't want it done willy-nilly: f some high-profile, reputable producers approached them about it, maybe they'd be more amenable.
Regarding Passion: Audra McDonald played Clara at Ravinia with LuPone as Fosca. Seems like a better role for her, vocally, but she probably wouldn't take the role now. If she was cast as Fosca, she would undoubtedly deliver an excellent performance - because she always does. Still, I'm not sure I see her in the role.
Regarding Anyone Can Whistle: I agree that it wouldn't work commercially - no chance. But I think an Encores-style producion is precisely what this piece does NOT need. After seeing the Carnegie Hall concert this year, I agree with Ermengarde that the piece needs a production with REHEARSAL and VISION. It needs a strong director who can grab it by the reins, and execute the absurdist tone with precision and cohesion. And part of that is they also need a cast who has enough rehearsal time to get into the comedic rhythms of the piece, to get on the same page enough to play off each other, and all work as an ensemble to achieve the right tone.
I don't necessarily trust Roundabout to assemble the right team of artists, but Roundabout seems like a good place for this kind of production, programming-wise.