Hm, I want something like this, except it doesn't write for you at all, instead it helps you build out your storyline, gives you writing prompts and feedback, maybe sometimes suggests ideas if you feel stuck, helps keep your character/story bible in order and text aligned with it, and gives you encouragement and visual feedback as you go along.|
Maybe add in some different "AI reviewer" type things, one to read broadly for enjoyment and give feedback, another as an editor to fine-tune particular sections. Even with these it should provide feedback, not re-written sections.
But I love the TUI approach and keeping things simple and organized for you, so you don't have to bother with all that. Bonus if it had some nice LaTeX / epub / PDF / html reader output.