No cores on entire Aquitane region?
Nope. I didn't see a mission available to get them, either. France gets Recover Aquitaine as a mission - can't remember the benefit of it offhand.
Excellent work. I forgot you can just detach a regiment and put the leader on it. o
Yup. Your idea would have been better if I was deeper into enemy territory, since a single regiment walking alone through France both ways is rather...doomed.