I have El Cap installed on a separate partition on an external HD so I can test several older applications that have not been updated lately. I can boot into the internal HD on my Mini, with Mavericks, and then delete the language files and also useless apps like Chess, Calculator and Stickies in El Cap.
Once I install El Cap on my internal HD and clone it my external HD I guess I'll be able to boot back and forth to delete language files and other stuff.
