Well - I flew night cargo for 6 years in Europe and I can say that 99,9 percent where the same and the same - real boring!. On top on that - unpleasant hours to work at.
If you wanna stay on the A300 I think it is only DHL, now able to offer you a proper schedule etc., but you will go to the same destinations time after time - the rest mainly in Turkey and most likely poor pay and roster. After a brief period on Pax B767, I went on to fly Business jets - I have good pay, roster and many new destinations !