Vallorick,
This may violate all of the "holy tenents" of ePub and Sigil.
An addition to allow the user to add semantics would simplify the making of MOBI without editing the content.opf file. This by itself would remove a lot of work. Once the MOBI file is built, I reopen the Sigil file and remove the Table of Contents.xhtml and every thing is kosher.
This would allow also a connection to kindlegen to produce a full-up MOBI file. This would easily fulfill the intent to eventually get to building MOBI files from Sigil. Kindlegen would be maintained by Amazon removing any future effort on your part.
This might even make HarryT happy.
