This is in part to inform about another comic book format and in part to consider if there are any easy parts of it that can be added to MComix.
The Android platform promoted by Google for mobile phones includes a few comic viewer programs. Droid Comic Viewer (occasionally referred to as Android Comic Viewer and shortened to "ACV") seems to be one of the more popular viewers. http://droidcomicviewer.com
They have created their own variation on the ZIP based CBZ comic archives and the format is in it's second iteration.
In the simplest terms it is a CBZ with an additional comic.xml file to provide some descriptions. The format also includes transition effects (even vibrate) minor visual settings such as the option to set the background colour.
[It does not seem to include any accessibility features such as text based transcripts or other annotations.]
I've found a discussion which includes an example of their earlier simple iteration of the format which just includes pregenerated thumbnails
thumbnails are stored in a subfolder z_tn/
It is a bit of a kludge but in the short term we might consider adding XML to the list of extensions that are considered "Comment files", until some future point where the Preferences dialog does something with that information. (Probably more relevant is that ComicRack includes ComicInfo.xml files and seems to be popular.)
Something I need to test out is how MComix works with ZIP files that have been renamed to ACV or renamed to any other extension besides CBZ or ZIP. (Tangent: From what I've seen of OpenDocument ODP slideshow files the filenames of Pictures/ are arbitrary and no useful ordering is preserved. I didn't get around to checking the file format specification to see if it was possible to force the file names to preserve ordering.)
Just thought it was interesting to see another CBZ variant, maybe it could become popular in time. Who knows.