The thing about overkill is, you can never have too much of it. Personally, I have had good success using Template Toolkit. The ttree utility sounds like a fit for your problem to me - it basically takes a directory tree of template files, fills in the values and creates a filled-in directory tree of files.

Of course, there remains the problem that all template systems suck, but at least Template Toolkit is not specifically geared towards HTML, which is a plus in this situation. Of course, the lure of ttree will be that it is too inflexible to handle all situations and hence you will be tempted to put program logic into your templates. Template Toolkit is a horrible language to program in, if you're trying to create expressions more complex than a simple addition (and even that...).