For the core path, the requirement is to find permission language files in the acp and mods folders. A couple of considerations:
1 - finder can only accept one core directory at a time
2 - we use add_lang() and ext_add_lang() for core and extension language files respectively

So to do like you said would either require that we set the core_directory as /language/ so it searches the entire language folder for permission language files or we search for each language folder (acp and mods) separately. If there is a way to have the finder search in more than one core directory, please let me know coz I couldn't figure it out