I don't have the answer for this other than large gates that could be opened but there needs to be a quicker way to let people leave the stadium if there is a serious weather threat. If there was an actual threat from the lightening, hail or tornado many people could be injured. We stayed during the first delay because as slow as the crowd moves there was no way we could have gotten out before the delay ended and it lasted about an hour.
Either this or the lightening is actually not a real threat and if that's the case they should play through it. The only ones that can get out are the players, coaches and officials.
I'm guessing your last point is right. Not a real threat, but from an insurance standpoint you have to have all scenarios covered for paid employees (both from the universities and partnerships). I'm sure the TOC's on tickets state the University is not liable for a lot of things.
And I'm fine with that. Imagine if you needed a "panic room" at every business venture to plan for a variety of things should they happen. It's not like the university would pay for an accident you got in while driving to the game, they gave the warning, from their it's up to personal responsibility. Cost would be insane.
Random story but I was once in a tornado warning at NFM in Omaha, and they would not let you leave the premises in fear of lawsuits. IIRC they stated if you leave you are leaving via your own free will and would not be allowed back on premises until the warning cleared. Which in hindsight seems asinine if people are looking for shelter.
All in all though, I'm glad the kids who got out there had fun, and they'll have a great memory of their time in school (both Iowa St. and Iowa students).