I read a rather biting commentary on APS film once. Yes, film, that stuff people put in cameras to record pictures before the existence of SD cards. This person, it might have been Ken Rockwell, had a rather snarky view of the history of film formats. Their shorthand explanation for nearly everything was "Kodak feels amateurs are getting more film that they
deserveneed so lets develop something smaller." Sheet film gives way to roll film, the early large roll film was shrunk to 6cm wide roll film 'for amateurs' (and ironically now viewed as a professional film format). 6cm is latched onto by the pros and the cheap stuff becomes 35mm film, using a format developed for movie cameras, just with the frame rotated 90 degrees (except on nifty half-frame cameras like the early non-digital Olympus Pens that the new Olympus micro4/3 cameras are named and ever so loosely styled after).
Only a funny thing happened. After hitting 35mm, the average person said, "That's small enough for me." Leading to Kodak banging its head against the wall repeatedly trying to move people down to something smaller. Disc cameras (because the average person obviously wants something smaller and is scared by having to position the film leader over sprockets)... Which died. 110 with its mini-cartridges. And eventually APS.
Ah, APS, where your frame had less than half the area of a 35mm frame, so they had to use superior film to keep a level of quality that people would accept. Only of course nobody was going to keep those film improvements for APS, they migrated to 35mm so the cameras that most people had could see a bump in image quality. Which is not to say APS didn't have some nice features, it did. The film had a coating that could record information magnetically. So cameras could record what frames had been exposed, want to change from color to black and white? Retract the film back into the cassette and pop in the B&W cassette, when you swap film again the camera can auto-advance to the first unexposed frame. It could also record on the film what aspect ratio you wanted, Normal, Wide, and panoramic. The date and camera settings could potentially be recorded magnetically onto the film for each frame. There was the previously mentioned higher resolution film stock. Markings on the cassette told you at a glance whether the roll was new, partially exposed, fully exposed, or developed (developed film was to be put back in the cassette for dust free storage).
None of the APS developments really required shrinking the film to below 35mm size. That was a decision made to allow for smaller cameras. So what if the smaller camera idea was put by the wayside and the camera companies said, "Let's do something that will get everyone excited with all around easily seen improvements." Take the improved film and cassette developments and instead of shrinking the film, bump it up by one measly little centimeter.
That doesn't sound like much does it. One centimeter. Slightly more than a third of an inch. Here is the thing, a normal 35mm camera frame is roughly 24x36 mm, or 864 mm^2 in area. Bump the narrow measure up by one centimeter and keep the same aspect ratio and you get a 34x51mm frame, or 1734mm^2 which is twice the area of the original frame. Considering that they had developed higher resolution films to make up for the smaller area of the original APS, giving a doubling ought to have allowed for quite a bit of marketing fun. Imagine an ad showing a 35mm picture blown up to poster size, and next to it a picture make on the new film. Visible grain on one, barely visible grain on the other (never mind that posters aren't normally viewed at one step away).
It would have essentially been an APS version of medium format film vs 35mm film. It would also likely have still allowed cameras that were nearly the same weight as 35mm vs the exercise equipment that medium format can be. And it might well have allowed film companies to add a few more years of mainstream success versus digital cameras. Probably no more than five even in an idea world. When people were buying 2 megapixel cameras it wasn't because they thought the image quality was matching their film-SLR, it was for the other advantages that digital had. But a more accessible medium or near medium format film might have kept the film market healthier for longer by giving people more of a reason to stick with film.
Or even stuck with the same film size and brought in everything else that APS had. That would possibly have been even more successful than shrinking or growing the film size. Those both would involve developing new lenses and camera bodies. a 35mm-APS version could probably have been made from nearly any 35mm camera body with only few changes. Nikon and Canon could have even done will with 35mm-APS SLRs by letting people keep using their existing lenses (even in a world with $12,000 DSLRs your real investment quickly becomes the lenses and not the camera body. There are plenty of lenses that could $1-2000 and up, and way, way up for specialty lenses).
Just some thoughts that popped to mind and quickly outgrew twitter posting size...