XF 1.2's built in template modification system means that add ons can modify templates easily and on the fly.... This means far less headache at upgrade time because there are far less actual edits.
In a crazy moment of madness, I wondered if this system could also be used to style / skin an entire site with zero actual template edits.....
OK, I'm just throwing this out there.... I have no idea what headaches this would cause but just thought the idea itself was interesting at least.