Thank you for the review. I do my best to make the saved pages as small as possible by removing the most of unnecessary HTML and CSS. It is already a lot of work, unfortunately I can't do more.

Edit: actually I can do more, check SingleFileZ here: https://github.com/gildas-lormeau/SingleFileZ

Thank you! Now there's also SingleFileZ :)
More info here: https://cup.aihedy.com/firefox/addon/singlefilez