I wouldn't be surprised if they stop giving AA benefits to EJet pilots, as they are solely devoted to the UAX operation, and there is no way for Mesa to justify that to AA/Airways (unless we ever get EJets for AA/Airways).

In the CRJ bases, it's easy to justify having all pilots on both systems, since reserves frequently cover flying in both systems.

If you're on the EJet (or going to it) don't be surprised if this happens--airlines do stuff like this all the time, and mainline mergers almost never result in better deals for any regional.