I think this is exactly where this should head. Solving the problem asked in this thread: Multiple views in MVC-like PHP Frameworks - #4 by s_molinari TSS really allows a much better method of doing this, especially where you have different people working on the front end and back end.
You’d still have two templates, one for the layout and one for the main content but rather than treating them like separate entities, you build the entire page with a tss targetted at layout.xml
contact.tss gets applied to layout.xml
title {content: "Contact Us";}
nav {content: template("main-navigation.xml"); }
.sidebar {content: template("latest-offers.xml"); }
.content {content: template('contact-form.xml'); }
Where this becomes useful, is that using the same .tss, the designer can run the same tss clientside and see how the contact form looks inside the layout.