So the folks on
bug 104 are talking about a different kind of template -- they want to have default page content for new pages.
However, they referred to what I want as "style sheets", which isn't quite as complete a thing as I want. I'd like to completely redefine the xhtml, including the link to a style sheet, including headers and footers, etc.
Pretend I posted the code from 104 to this bug, and keep working here ;-)