Since we don't know what kinds of pages there are or are not, page breaks are useless. We do have syntax for a chapter break, though: "===".
No. Please re-read my examples and have a look at some source code in Wikipedia and Wikisource for valid applications of my suggestion.
There is a very good reason for floating elements such as images into the next chapter by default - even on printed books.
But I said: There are certain reason where it is necessary doing so and many people are doing so right now with crappy syntax. You won't stop them but you can help them making it better in future.
Ok, so === isn't quite what you want. You probably want <div> tags. A div tag is designed to separate different parts of the content, which is exactly what you are trying to do.