We currently have translations for languages which are used in multiple countries, and would like an easy way to make country-specific adjustments without having to have 2 or more separate locales. For example, we have German, and use it in Germany, Austria and Switzerland. We don't want to have to maintain all our translations strings in de-DE, de-AT and de-CH but would prefer a common "de", with the ability to make overrides in de-DE, de-AT and de-CH. If we could create de-DE, de-AT and de-CH and be able to set their fallback language to "de" (and then also have nl-NL and nl-BE with fallback to "nl", and fr-FR and fr-BE with fallback to "fr" etc) that would solve it for us.