Two feature suggestions:
1. An option for specifying a block of CSS code to be inserted into the ebook stylesheet (e.g. @font-face headers for specifying a font without having to embed it into each ebook file), avoiding the need to open, manually edit, and re-zip the ebook.
2. A search-and-replace option for preserving the text/image/object found in the "Search" as part of the "Replace", similar to the "^&" special character in MSWord.