I have implemented a first pass at language pages, these exist in hitherto unused urls:
For example, all English translations:
https://suttacentral.net/en
When there are many translations, they are broken into divisions:
https://suttacentral.net/en/dn
In the case where there is a so-called “division length text”, it continues to work as it presently does, that is it takes you to the text and doesn’t attempt to generate a division page:
https://suttacentral.net/en/lal
It is also possible to put custom content on a language page, as I have here:
https://suttacentral.net/pl
(Note: This is all from http://sasana.pl/suttacentral - with one exception, I google translated “Early Buddhist texts, translations, and parallels”!)
Under the hood, making a custom page involves creating a template templates/language/<isocode>.html
Note that these pages are presently active on suttacentral.net (I’d considered making them only active on staging, but I don’t see them doing any serious harm) but at present there are no links to them, if you manually create the url they will work.