The same way that people can switch between deskop and mobile (or get it assigned to them based on their user agent), we could have a mode designed for no-JS browsers, which would allow us to get rid of no-JS support in both desktop and mobile.
Let's call this new mode "light" mode.
The amount of CSS this mode would include is debatable. It depends which objectives we favor. If we're looking to achieve to best performance possible, we'd have to either get rid of all CSS or inline it in the head for every page. If we want things to look as rich as the main site, we'd still have some CSS linked from the head. It would be interesting to explore how large the CSS would be if we only kept the amount needed for survival.
- this mode should provide a much nicer experience to screen-reader users
- browsing wikipedia in text-based browsers would also be a better experience (eg. ebook readers, command line)
- if we go as far as not having external assets in the <head> (by keeping the CSS to a survival minimum inlined, for example), it would be blazing fast, in fact in that respect it could become a true alternative to the mobile site for users with <3G mobile connections
- by removing the burden of no-JS support from the desktop and mobile site, they could make use of a lot of modern tech that is currently impossible due to the requirement of the page working without JS. We could make both desktop and mobile much faster.
- some browsers put in the "light" bucket would be served an experience far inferior than the browser's capabilities
@Ckoerner found a similar idea done by NPR: http://thin.npr.org/ given that they deal with audio content, they went text-only, but there's no reason why we couldn't serve images.
@santhosh pointed us to the fact that google now processes websites to achieve similar results in India on slow connections: http://googleindia.blogspot.in/2015/06/faster-and-lighter-mobile-web-pages-in.html