It probably wouldnt work, or theres some major flaw in my thinking but..
Couldn't Plus! when installing or w/e find the system's language (from the registry perhaps?) and if it doesnt match the list of languages contained in the installer, maybe pop up a
simple message giving the user a webpage with all the translation files (a forum post perhaps? and maybe an "official" page too, so if one server is down then at least they can try the other?)
Or maybe they can select "other" from a language list or something which does roughly the same thing.
I think it could work, but it would need better thinking through probably