I've again reached the conclusion that I really want a blog engine that is powered by XSL.
And then right after I come to that conclusion, I realize that Movable Type Open Source could be customized to support such a goal, and that I've already started Mutable Times for this exact purpose. I really need to dig into Movable Type and get started.
First thing I'll need to do is update the MutableTimes codebase to catch up with the developments which have been going on with MTOS. After that, I can take a try at getting xsltproc to act as the published instead of the homegrown perl powered MT templating system that MovableType uses.