Also, I just don't hear other US healthcare professionals talk so much about international practice rights (i.e. dentists, optometrists, podiatrists, pharmacists etc.) I'm sure similar barriers would exist for them, versus their foreign country counterparts.
Again, fluency in a language would be first on the list of requirements. Being able to stumble through a conversation is one thing, but being capable of interpreting technical literature in a foreign language seems to be quite another. And fluency should be a requirement. (though many FMG's practicing in the U.S. don't appear all that fluent).
So, ASIDE from missionary work and those fluent in another language, I don't quite understand the interest in oversees practicing rights (other than simply advancing the international standing of the U.S. DO profession etc.)