The examiner doesn't have to be French, you just need an examiner authorised to carry examinations under the French authorities. My school has examiners authorised to carry exams under the Italian, French, Finnish, Norwegian, Dutch, Belgian and Irish authority.
You just need to do the SOLI process, which is a transfer of medical records from country A to country B which will then issue a new medical. You won't have to worry about your ATPL scores.