After looking at a lot of web app frameworks, Johnvey put it most succinctly: “none of them are complete. You’re better off with an off the shelf solution”. He also pointed me to textpattern, which I’ve set up here.
So far, I’ve been quite productive with it. It’s templating system is a bit odd (or rather, the terminology seems somewhat poorly chosen), but it is much more structured than WordPress’. I’ve already been able to add a couple features that I’ve wanted with WP (like short comment excerpts appearing next to each post) without writing much code.