I don't think the ME model would work nationwide. Right now, they have a good niche that doesn't require them to compete with rock-bottom airfares. They "own" a lot of routes by themselves. (From Kansas City, I've flown them about a half-dozen times: always because they were the only choice, and always at a somewhat premium fare.)

If they went national, they'd have to compete with low airfares, and I doubt they could be profitable.