I am pleased to read that you have not given up on your Clip Sport. I enjoy using my various Clip Sports since buying my first over 2 years ago. I have experienced a variety of problems using m4a files. I usually make the extra effort to convert my purchased m4a files to mp3 format and I like to use ID3 tag format v2.3 ISO-8859-1.
I really doubt there are programmers / engineers affiliated with SanDisk who will be working on Firmware updates for the Clip Sport.
Here is one suggestion for you to consider: Try out a few software programs that can automatically convert a batch of m4a files to mp3 files with your desired encoding specs. Maybe you will get lucky and the embedded artwork will be properly displayed in the converted files? You could test-drive a few batches of audiobooks that you want to play now, Then once you have a satisfactory process you can let your computer work unattended for 1-2 hours a day as needed?
My current favorite batch audio file converter software is “Switch Audio File Converter” by NCH Software.
http://www.nch.com.au/switch/index.html
This software has a wide variety of settings including an option to save the converted files into the original source folder(s).
