Retailers design huge parking lots for one weekend. We can have a pedestrian bridge for 6 or 7 games. It would really help the traffic flow and be a cool design.
I'm not sure if building it would change the legality of open containers as you cross the street. You can have open containers because ISU allows you to drink on their property (which is against state law as they have a site-specific liquor license but it's overlooked) while the City of Ames does not allow open containers on public property. Crossing the street still means you would have to cross City right-of-way where city law applies. The local ordinance would need to be changed to allow open containers in specific parts of town on specific days, which may be a political battle. On the other hand, you don't want to bite the hands that feeds you.