Not sure about them performing something by the Mavericks. Malo(like Orbison) has an ethereal quality to his voice that adds a lot to the Mavericks' songs. I like the Mavericks' version of "All the Heaven Would Allow" even better than Springsteen's. I think the Mavericks are great, but the Mavericks without Malo--not so great.
While I'm on the subject of what probably shouldn't be done, everyone should steer clear of bluegrass(although Taylor would have an excellent voice for it) because there's no way the Idol house band could pull it off.
Good point! In fact, I was wondering if bluegrass, rockabilly, country blues, country rock etc., all fall into country or not? I would think they would, but shoot, don't the lines get kind of blurred at some point?