My airline would be very simple. I would fly one type of aircraft that's configured for high density seating for low-fare operations.
The jet would probably be a 737 a 757 or maybe, and yes I would suggest it, possibly an Airbus 319 or 320 or 321.
I would probably have one hub city, probably Memphis, becuase I don't believe they have too much low-fare competition there.
(Wow, I'm starting to sound like I want to create a Jetblue-influenced knock-off, but this airline would probably fail terrribly. Maybe I'd develop a fractional business jet company flying a series of Citation jets, ranging from the Bravo to the CX.)