Moodle could go one little step further with support for personalizing, localizing, and/or extending language files. If I create a new language, for example en_local, to replace a few of the standard strings or to add an extra string, then this language shows up as 'English (en_local)' in the language popup menu. Not very professional and potentially confusing to some users. I'd like to use en_local as language but still have 'English (en)' in the menu. Our users do not care whether the texts are localized or not.
<br><br>Moodle could designate the _local locale suffix as having a special meaning: designating a language customization. It'd automatically strip this suffix from the language code when building the popup menu (or simply use the parentlanguage string). This would also make such language folders easily identifiable as not part of the distribution.
<br><br>I believe this would also make it easier to add extra strings for a given site, which is particularly useful for true multilingual sites, offering an alternative to multilang filter for fixed web page elements. I suspect that using a custom language pack is more efficient than multilang filter.