Nicely said BlueAfrica. Its true that the NCAA wants local co-pilots, but you only have to look around to find out that this is not the case. NCAA is not suggesting you train an ab-initio and put him/her on the right seat. You will also find out that almost all the companies running the local routes are owned by Nigerians with the exception of Aero Contractors.
Most of these expat companies you are talking about deal with the oil sectors. The company am working for just employed two expats co-pilots and are currently giving them type (company is owned by Nigerians).
Government in Europe and elsewhere around the world have employment laws that deal with these sorts of issues. Africa unlike other places actually welcomes and respect expats.