Three days ago, I said I wanted to mock up a way to toggle the default chapter headers on and off. Since then the response has been incredible-- though I'm not sure how much of that is just because it was on the first comment page of an archive news post. Thankfully! Thanks to everyone else in the thread, it's looking like this project might be much easier than I thought it would, which is a HUGE RELIEF.
A big big contributor to that is this tutorial by C Ryan Smith, linked by Callmesalticidae, explaining how to use workskins to do the very thing I'm trying to do! And it's really short and easy to follow, which is very very helpful.
Also, a few people mentioned
So! Here