Not to be rude, but are you asking if you are considered a real pilot or semi pilot if you work for Mesa? It just seems like a silly question. If you feel that a regional airline has an inferior level to the quality of pilot and training than that of a major, passing the checkride should be easier right? What I mean is that a pilot is a pilot and expected to perform to the standards put forth by the FAA no matter which carrier you are at. Of course a legacy or major would see that as a flaw in your abilities. If you can't hack it at a regional, then why should you be able to hack it at a legacy?