This is exactly the problem Web Developers saw in 2002 when Wired redesigned this structure by separating CSS (the presentation) from HTML (the structure). So we have known this yet when we are dealing with this on a Large Scale in an Enterprise it is ignored or just thought to be un-doable because of the solutions that are at hand.
It is very similar to challenges with large enterprise web deployments. Backend applications are in a lot of cases pushing out the presentation, structure is down to the mish mosh of multiple applications with inconsistent views, and when the presentation is separated it is complete out of the hands of the organization to make changes to it. So why has this not been addressed on a large scale?