Or maybe it can render on Page/en or whatever the page language is. Ultimately meaning Page/en and Page get their rendering swapped

In my mind, that's something you don't usually need to do, so it would be fine as a URL parameter or a special page or something similarly unintuitive. But is there something I'm not thinking of? Probably...

Had a possibly very good idea: have the main, untranslated URL for the page render in the user's UI language. Then all the links can just be normal unmodified links to the main page URL!

I'll send a gerrit change(s) with the json file(s) later.

I suspect it actually should be added to https://gerrit.wikimedia.org/g/translatewiki/+/master/LanguageSettings.php instead.

I'm trying to figure out how to submit translations for Toki Pona, but it's missing from the dropdown on Special:Translate. Should it be added there?

Some translation work has been done recently starting with the old /tokipona data, which can be found here: https://github.com/tbodt/mediawiki-tokipona/. It would be better to delete the tokipona data and import this instead.