I think what you've accomplished here is great and love where you're going with this extension. Here are a few annoyances I've run into that I haven't seen listed.
1. Clicking the + button to create a page is sporadic. Sometimes the window opens and some times it take several clicks for a window to open. This is even worse when you click the + button to add fields.
2. I seems to me the Add all should be at the top instead of the bottom for a long list this is annoying especially if upon releasing it doesn't add anything. Which with a long list seemed to be 90% of the time.
3. Is there a way to prevent the page building from adding any css files to the page? I've taken all the styling used and made it one linked file.
4. How do you adjust the HTML Editor values before building the page. It looks like it just takes a default value.
5. If you add the Datepicker on build the link to the styles is broken.