I'm not interested. There's just too many finicky bits to overcome when going ncx/nav to html (as opposed to going html to ncx/nav). Mainly the situation where the h tag doesn't exist and needs to be created. What level does it get created as (3,4,5,6)? Where in the html will it go (outside/inside an adjacent div/span)? Can't put it at the top because not all chapters begin with a brand-new file. Does it need a class name for styling purposes (display: none)? If so, will I have to parse all css classnames (after determining which external css files are linked) to determine I'm not reusing an existing class? I'd also need to check any css that might be included in the header of the html file to be sure. Otherwise, I'd have to resort to using uuids for class names (after making sure they start with a valid character). And in my opinion, that gets uglier than the issue said plugin is trying to fix--only very occasionally.
Breakage is not an option if I'm to create a plugin. And unfortunately, there's too much that can go wrong when attempting to reverse the automatic toc generation process. Especially if doing so requires generating html that doesn't exist. There's waaay too much to account for (properly) for all the more it would be used.
Someone's free to use all of the problem areas I mentioned to work on it if they like, though.
