Let me preface this by saying (despite the words I will likely use) I am not disparaging anyone's choices or opinions.... I'm simply trying to illustrate a different way of thinking about the situation that people may not have thought about.
I have constant image width too, but mostly because I am width limited in my projector room, and have more than enough vertical space to have a 138 inch 16:9 image without hitting the ceiling or the bottom of the image hitting my speakers. (120 inches wide, also makes a nice sized 2.37:1 image too).
IMO there's no such thing as a "width limited", if you think that you're too focused on "inches" and not thinking enough about the overall system and experience. The reason I say this is a lot of people still think about their Home Theaters like they do a TV. We've been (unintentionally) conditioned to think about TVs in terms of more inches is better/bigger, but TVs don't have aspect ratio to consider (they're all the same) so for that it works. However home theater is all about the experience and how the whole system works together, and that system is not just the screen, includes the room, projector, seating distance, etc.
When you setup an HT, IMO "is my room width limited" is absolutely the wrong question to ask when trying to decide whether to go scope/CIH or not. The right question to ask is whether you believe Jeopardy, the evening news, 2 Broke Girls, or Sharknado should be larger than Lawrence of Arabia, The Matrix, Star Wars, etc.
If you believe in the concept that scope movies are meant to be larger, then you can absolutely have a great CIH setup in a room of any width, you just have to ensure your seating and everything else all work together well. There's no such thing as "width limited" or "too narrow" except in one's own mind.
The way I see it, isn't that Jeopardy would or should be bigger than Lawrence of Arabia, but that IMAX format movies and games would be bigger and have more vertical space. I can always shrink my 16:9 content a bit if I want it smaller.
Jeopardy isn't IMAX though, and while you "could" shrink 16:9 down, do you, and do you have the masking to do it? That said, I agree with you about IMAX, which is why for a long time I've said CIH+IMAX is the "ultimate" in home theater. It is, simply, the largest 16:9 screen you can fit, but most of the time it's masked down to 2.37:1 and run as a CIH/scope system. But when you've got IMAX content you can open up the masks to get the IMAX experience.
The number 1 problem with CIH+IMAX though, beyond the need for more masking, is the lack of content. At least for me (who doesn't collect IMAX documentaries) I've only got one, maybe two movies with IMAX content. It's just not worth it for 2 of 200 movies. On top of that it is technically impractical for me, since my projector doesn't have the zoom necessary for the zoom method so without extraordinary measures, it's just not possible.
I love my VC lens but it's definitely a huge step down in size for movies and games in 16:9 when using the 4:3 shrink method.
While I understand, that for 16:9, IMO it's a bigger sacrifice to go from huge screen, arbitrary content (TV, streaming, games, etc), to a 25% smaller presentation of a an epic scope film that was meant to be 33% larger instead. Or, to look at it another way, should be 78% (relatively) larger than it is.
For me, movies are the most important thing I view in my HT, but I do watch a lot of TV in there too, and when I have friends over for a movie night we usually watch some favorite TV and play some games before the feature presentation. If I went with a 16:9 screen, epic movies like The Matrix, Star Wars, Lord of the Rings, etc would be
the least impressive, thing ever shown in my theater, and IMO that is just wrong. While I really like Top Gear, Forza, and Halo, I don't want them to be more impressive than Star Wars, I mean if this isn't one of the largest most impressive things shown in a home theater, is it really a theater?