I'm reluctant to call this the 5th way, since it's closer to the Crouching Tiger Hidden Dragon dilemma, but it's worth noting. A director can always cast the foreign character as a native mental deficent. I guess the best example of this is The City of Lost Children with New Yorker Ron Perlman, where the filmmakers had him speak in rather broken French. As an aside, it's always oddly easier for English language filmmakers to put non-English speaking actors/characters in their movies.