I don't have a whole lot new to add, other than to echo a few others' opinions:

Absolutely contact Emerald Coast Consulting. I know plenty of people who have had GREAT success with them. They will teach you a lot about the interview process, and evaluate you on several different aspects of your experience, personality, etc and give you helpful ways of saying the same thing, but in a manner that will be best received by the interviewers. They will do over-the-phone interview prep, but if there's any way you can meet with them in person (they prefer this) definitely do it.

I also agree with not applying to airlines you do not want to work for. I agree that interview experience is helpful - but you've already been through two. I think you know the drill by now, and Emerald Coast can help get you prepped for any future interviews. I have it on good knowledge that many airline hiring departments talk to each other, and when they ask you, "Have you interviewed with anyone else?" - often, they already know the answer to that question. You don't want to put yourself in the position of having to explain why you've been on 6 interviews and turned them all down (or worse yet, lying to them).

And I also agree with your point - worse case scenario, you never know - you may want to get hired at that random airline sometime in the future. In this industry, for all you know, 6 months from now they could be awarded some huge contract with a hub in your home town, and then you'd seriously be regretting it.

I've got to commend you on something that I've noticed in your posts... No where have I detected a bit of defensiveness or justification in your attitude. I think that's awesome. You're being self-reflective and asking for help, and you're willing to do whatever it takes to get there. Absolutely, DO NOT GIVE UP. With that attitude alone, you belong in this industry. Your time will come. I got turned down by my #2 choice regional, and when it happened, I was devastated. I look back on it now, and the way things turned out, had I gotten hired, it would have tanked my career. It was one of the best "worst" things that ever happened to me. Best of luck to you.