Mercury, I took this route myself. However, I was a FA at a regional airline and then was hired as a FO. In your situation (FA at a major and looking to move to the right seat there), it would be a lot harder. I would consider leaving, quite frankly, but on good terms. It will make your trip to the regionals (which is almost required) a lot quicker. And with experience and good history at your current company, you may be able to shorten your stint at the regionals, which is also a bonus. Good luck!