One of the three AAG regionals is already run by an AAG Corporate Officer. The other two just have their own CEO's.
The books have been slowly morphing to AA standards for decades. They're so close now that OE for an Envoy flow is pretty much airplane stuff only. Using the computer, DECS/RES, the apps, EFB, and company policy and procedure are so similar that the AA CKA say it's the easiest OE to do. Once they get the other two regionals on board it will be time.