Just in case you run out of ideas, I like the idea of something like Focus Mode.
What I mean by that is a writing experience much like we have now in full screen, with no distractions, but in addition it would display just the text we're working on, without showing the page breaks. I feel it can interrupt the flow if a page break comes up and I find myself constantly at the very bottom of the screen.
I'd love it if Focus Mode could just focus on the last few lines of text, no matter if there was a page break or not, and give me some room at the bottom. It would be like having an endless piece of paper that you keep typing on until you're done. This means less manual scrolling, and pure typing.
Because sometimes, it just flows, and you want to let it all out :-)