I am working with a visibility impaired charity to produce their website - I am using foundation as my theme. As standard among websites for visibility impaired users alongside the standard website they have a visually impaired version. As an example please see:
The website you link to does seem to have duplicated pages. I think it’s your request to not-duplicate that makes things more complicated. However, you could have different CSS for regular vs. high-visibility pages. You’d have to take care of creating the CSS yourself (perhaps with help, or with support from others who do similar sites).
BTW, I’m not sure what’s supposed to go (or not go) in a high visibility site but the example you provide is certainly more “visible” but it also seems much more awkward to use. Maybe it’s all done perfectly fine but we might be able to help you more if you gave the core parameters of what needs to go into a high visibility site.
Essentially as you have picked up the high vis version is devoid of images and unnecessary layout - so it is easier for a visually impaired user to read it with a screen reader.
I had in mind a solution like you suggested to switch the stylesheets, but didn’t know where to start in doing that with the foundation theme, especially as it would need to store that setting in a cookie so that when they navigated from page to page it went to the high vis version.
