I propose that we add 100 or so MediaWiki core messages to the "most used messages" list, so that we can give a single link to that list and translators will know that it's enough to get their first export to the MediaWiki core repository.
(After the first export, addition to Names.php etc. is "automatic" because Raymond is paying attention and multiple people are watching https://translatewiki.net/wiki/Translating:MediaWiki/New_languages .)