I've created a new version 0.27 with the following changes:
- NEW: Extract and save source zip files included by kindlegen as kindlegensrc.zip.
- FIXED: idx:entry attribute "scriptable" must be present to create entry length tags.
- FIXED: Don't save non-image sections as images.
To ease development I've also pushed my git repository for the mobipocket script to github. Feel free to fork it if you want to improve the script: