How we could all benefit from Betagov's accessibility work

Accessibility is the subject of the latest post on the Government Digital Service blog: having had their fingers burned in the ‘alphagov’ phase of work, by consciously ignoring the subject, it’s clear they want to be seen to make it a priority into the beta phase.
Léonie Watson writes:

Tom Loosemore has said: “… we want to make the most easy to use, accessible government website there has ever been”. Those of you who know something about web development on this scale will understand what a challenge that is. Those of you who know me will also recognise it’s a goal I thoroughly believe in. So, what are we doing to achieve that goal? Simply put, we’re planning accessibility in from the outset and documenting the accessibility steps we take throughout the website’s lifetime.

I’ve posted a comment on her article, which I’ll reproduce here for the record. You’ll instantly note a common theme with my recent inflammatory post about departmental publishing.

As you’ve noted, accessibility is very hard to get right: you’re conceding that you might not even score a ‘perfect 10’, even though you’re ‘planning [it] in from the outset’. And as [previous commenter] Keith says, for small organisations, it’s prohibitively expensive to even buy the rulebook, before you even begin to implement the rules.
If government is hiring experts, consulting widely with users, and (hopefully) delivering exemplary results, it seems like a tragic waste for the benefits to be locked into a single website.
Wouldn’t it be fantastic if one of the outputs from your work were to be a reusable, customisable front-end theme for an open-source, widely-used publishing platform, like WordPress or Drupal? You could enforce certain ‘must have’ accessibility practices in the page templates, whilst still giving people plenty of scope to make it look and feel like their own site – via a parent/child theme arrangement, or a ‘theme options’ screen.
You could then release that theme publicly – giving web developers everywhere a robust base on which to build their sites. Imagine all those common accessibility headaches being solved, before the first line of custom code is written.
(I’m not suggesting this would solve all problems instantly, of course. And there’s still plenty of scope to cause all sorts of new problems in, say, a child theme’s CSS. But you’d certainly be giving people one heck of a head start.)
The fact is, very few organisations have any real motivation to get accessibility right. But Government has a moral obligation to do so. And you’re spending our taxes to do it… so I’d argue we all have a right to enjoy the fruits of that labour. Central and local government, public and private sector.
Issuing a list of rules seems a very old-fashioned way to encourage / enforce good practice. You have an opportunity here, to do something much smarter than that.