But serving these from PG this makes a big file even bigger
A big file? What definition of big are we talking about? What's 500k between friends any more? Both Epub and Mobi support page numbers; why don't we translate page numbers from HTML to those formats? It might take a standardized format of page numbers in HTML, but at least you're supporting the people who want page numbers. RST doesn't support page numbers, it doesn't support sidenotes, it doesn't support math. And given the nature of the spec, whatever new book-thing comes up, it probably won't support. I don't particularly feel well-served by how TEI-Lite has been dealt with at PG, but I'd much rather have an incredibly rich format like TEI-Lite that has to be distilled down to fit HTML, then a format that limits me to the features that are convenient in Epub today. -- Kie ekzistas vivo, ekzistas espero.