Most of the RJ guys in my New Hire class had some form of Check Airman on their resume. It'll take you a few years to upgrade and by the time you have 1000 PIC it would improve your chances to go get a Boeing type at an ACMI carrier, BUT I wouldn't take that gamble of giving up a guaranteed job at American. Even if it's 8 years until you flow it may take 4 just to upgrade and hit 1000 PIC... Maybe more.