There seems to be a misconseption about licences. JAA and FAA are ICAO. All 3 are accepted. However JAA is preferred over FAA and other licences. Might find it difficult to get a job on a Gabonese ATPL. But if you hold a JAA ATPL and are trainable you might get in with Chieftain time or just flight instructing under your belt.
If however you are of a non-European origin (Not a citizen) and do not have a full JAA licence you will have to have appropriate type rating, time in type and a minimum of 1500 hours flying in JAR25 aircraft to qualify.
Hope this clarifies things a bit.
AD