A few things from someone without too much experience, so take it with a grain of salt...

Get a degree that will serve you well if for some reason your flying career is suddenly no longer an option...like engineering.

Also, I had a friend who went straight from highschool to a flight academy to a regional and was flying for a regional while only a few years older than you. Sounded great at the time to me while I was still battling books in school, but looking back, now I'd much rather serve in the Air Force and then go to the airlines than go straight there. Even as an Army puke, my flying has been more fun and exciting than my civilian flying ever was, and learning to fly in the military is really good experience. I only bring up the military because you brought up possible boredom with domestic routes w/ SWA. 30-40 years of flying the same routes seems like it would get very boring.

Like you are doing, keep your options open. The airlines are kind of hard to predict, but SWA seems like the place to be today. That "soft spot" could go away very fast if things change for SWA a couple years into being with them and you have a family to feed and bills to pay. Or things could still be great. Just don't get too dead set on it years before you will even be applying.