Thinking more about this: ZIP files can be set up to have the data on whatever alignment of one's choosing (as noted in the reddit thread). Integrity checks can be done in parallel by doing them in parallel. mmap is possible just by not using zip compression.

The aspect of integrity checking speed in a saturated context (N workers, regardless if its multiple workers per file, or a worker per file), CRC32(C) seems to be nearly twice as fast https://btrfs.readthedocs.io/en/latest/Checksumming.html

ZIP can also support arbitrary metadata.

I think this could have all been backported to ZIP files themselves