Jang,
In my experience, the customer pays for translation one way or another... The translation outfits I've dealt with support Frame files. So the customer can either pay for a good translation in the native environment or pay you to clean them up.
As far as sending the graphics along, if you train your translators to select the Ignore Missing Files option when they open the files, your existing paths will be preserved. (As far as file transfer size goes, most translation outfits have FTP sites for file transfers, or you can use any of half-a-dozen "large file" transfer outfits to do the work on both your and the recipient's sides.)
That side track aside, because nothing can really be exported directly from the MIF files, someone, somewhere, is opening them in Frame. They may then be exporting to Word, text, or something else, but someone in your translation chain is using Frame. The problem is likely occurring because whoever is doing the work isn't round-tripping the files properly, so some information may be corrupted.
In any case, if you're getting MIF or Frame files back in, you can edit them in MIF at that point to correct the paths.
Art