In many industries, writable PDFs are commonplace and aren't seen to be a problem because people in those industries don't see any problem with using Acrobat.

In many industries, writable PDFs are commonplace and aren't seen to be a problem because people in those industries don't see any problem with using Acrobat. If you want to unseat Acrobat and PDF, I think you'll have to provide something that has equivalent or greater power. As for multi-image container formats, I think we already have that: cbz/cbr. Just a zip or rar archive with images in it, to be displayed in order by name. This 'format' is in common use already for scans of comic books. There are numerous viewers you can use to open and browse these files. Something to consider though; accessibility. A screen reader needs to use OCR to read these files to people with impaired vision. PDF files aren't fantastic for screen readers either, but they're much better than just a JPEG. I'd love to see some sort of subtitle system for images (I think mpv could probably overlay a subtitle sidecar on a still image, but that's not widely supported. Text-based subtitles formats are easy to wire into text to speech though.)