Is this slightly insane? Perhaps… It'll probably be difficult to write each section assuming it might be your intro to the game, while balancing not feeling too repetitive or spoon-feedy with not requiring too many cross references too early. But I still think the layers of flexibility is worth it!

This predicament is precisely why, once I break into making bigger games, I plan to eschew one big book in favor of a bundle of themed booklets. Rules, Chargen, Setting, Play Tips, GM Stuff — whichever you wanna see first, just grab it! (I think it'll also make cross-referencing easier.)