That's a really good point...these are "white elephant" theatres that are challenging to make work. I'd also add the Lyric to that list, except that I haven't been inside since the renovations and am not sure what that will be like post-HARRY POTTER. And I wonder how hospitable the New Amsterdam will be if ever there comes a time when Disney doesn't have a production to run there, but the Palace always seems to have an occupant and the layout is similar, so maybe it'll be fine.
Had anything made money in the Gershwin or the Minskoff prior to their current long-running occupants? I imagine there might be more interest in the Ambassador, simply because it could be made to work for more of a variety of productions, but it's still such an awkward theatre that I'm sure it would continue to be at the bottom of every producer's list.
I wish it were possible for some enterprising real estate baron to build 3 or 4 more Booths or Music Boxes or Jacobs or Helen Hayeses. I suspect that they'd be occupied more than they'd be empty.