If they show movies on the thing, I don't see why they wouldn't try it for a football game. Definitely a cool idea. And as far as the staff costs, that could be kept to a minimum - it's not like you're going to have 55k show up. I'm sure there would be licensing issues, even if the school doesn't charge for admission.
I would REALLY be interested if they opened up the field, so that you could basically tailgate and watch the game on the big screen. I realize you can't let the field get torn up for the next week, but it would be a cool thing to try for a big away game, like Bama or LSU.