Just so this doesn't get forgotten (which is easy for me to do), I have read that there was a considerable 'Celtic' population in Egypt that lived under and served the Ptolemic Pharoahs. They apparently embraced Greek gods, and were buried in Egyptian tombs...celtic inscriptions have been found in them.
Sooo...I think it would be nice to 'duplicate' a unit or two of nice Celtic units for Egypt to recruit in the region where these Celts lived only.