Basically Russell, I know what you're after, but it's just not a really good idea for anyone except those who somehow want to project a taller image than the 2.35 frame like you're doing. It still gives you a narrower picture when it goes to the IMAX stuff, like the bottom example in the pic below....
...whereas if you look at the cropped version for full 16x9, what are you really missing? More space above his head? It's much more bothersome to sudden;y go to a narrower picture frame, even if taller.
Instead, maybe you should push for something that somehow increases in height projection/resolution when the shots call for it...or a new higher overall picture projection size for movies with IMAX footage in it, with the only downside being a very narrow 2.35:1 picture.
...not that there are a lot of movies aside from TDK and TDKR that use a lot of IMAX footage. But overall, tat one example with the pillared/sidebars of black is the least desirable thing you want to see out of all the options...even if projected....if for nothing else that it's combined with other compositions which are wider. It makes it look/feel like there's something missing from the sides. The side-to-side size should stay the same throughout the presentation...that's what they're shooting/composing for. The extra height are for screens/projectors that are equipped to do that while keeping it the same width as the other stuff....not to squeeze narrower into a rectangle. That would certainly bother the heck out of me if I was in a theater, and the picture would get narrower for some shots...regardless if it was taller. To get what you're going for, it's better to hope for a larger/taller format and more IMAX-originated material...or at least all-IMAX-shot movies that stay all in the 1.44:1 IMAX ratio. Otherwise, might as well utilize the entire screen area/width (the larger of the two dimensions) of your projector's/HDTV's native resolution and not fret about extra image material that's cropped out if there's nothing there to begin with.
We're talking about two very specific examples...these Batman movies...both of which are shot to be great in IMAX, but not to be lessened by what you don't see in full IMAX. But yeah, if you think there should beBluRays that stay in 2.35:1 the whole time, sure. I say have a setting that will put the letterbox bars in if you want them, but go full 16x9 if you don't.