A mobi2html that explodes MOBI to HTML would also be useful. It would obviously only work on DRM-free PRC and MOBI files. The easiest option would just be to extract the single HTML file and the images, with the images correctly referenced in the HTML. Better would be to extract the .opf file from the HTML preamble. Note that mobi2epub would then be a simple addition, or just use the existing
oeb2epub.py in combination with mobi2html.