I don't think this method fits camera raws particularly well. The real world is noisy, so it becomes very unlikely that you would ever hit the two most compress

I don't think this method fits camera raws particularly well. The real world is noisy, so it becomes very unlikely that you would ever hit the two most compressible methods of QOI, (1) pixel value repeat or (2) index into one of the previous 64 pixels. QOI works really well for 8-bit screenshots, with lots of pixel-values repetitions. No such luck in noisy 14-bit real-world images. Also, this format was designed to be as simple as possible, and is byte-aligned, only handles 8-bit RGBA. You would need a different design for 12/14-bit RGB or RGBG (Bayer).