Not really. The hardest part is getting the activation bytes and even that is actually quite simple and you only have to do it once. For the actual converting I

Not really. The hardest part is getting the activation bytes and even that is actually quite simple and you only have to do it once. For the actual converting I have a bash script that can convert all the aax files in a directory and convert them to a m4b format with all the metada intact. Using your approach you would have to manually set the chapters and the cover art. I have thousands of hours worth of audiobooks but even if you only have a single 10 hour book I think this approach is still the easier of the 2.