I don't work for an overseas outfit, but have applied and been invited for an interview (twice) with Cathay. I have your run-of-the-mill ATP. From what I gather, if you make the grade with CX, in training they will get you through the appropriate hoops to get the licenses from the Hong Kong authorities. Not sure about elsewhere...
So, I would save the $$ on getting any sort of FAA ticket converted to "international acceptance." Any non-US company that hires Americans has some kind of process in place to make you legal. If you're looking to work for some foriegn outfit that does not have that US citizen hiring process in place, then I'd say your biggest hurdles are citizenship issues, not flying licenses.