It seems there's a huge opening in the market to make an end-to-end publishing solution. We're all taking this scrappy approach* to making our books work cross-device. It's something I'd gladly pay for. *I wrote about my pipeline here: http://startupframework.tumblr.com/post/36675629669/format-e...
The biggest problem I've recognized with epublishing is that you have to get the formatting down perfectly, and usually that requires a lot of work by hand making sure your input HTML file is exactly as it should be. When you control how content is inputted to a platform, it's much easier to automate perfect-formatted rendering of that input HTML file, including TOC by inference.