This is all going to look fantastic when finished before the season starts. Leave the hillsides, it what makes JT different. It let's parents of younger kids still attend games and helps to cultivate the next generation of fans. Don't over build the stadium in an era when season tickets are going up and more people are just as happy to tailgate at home and watch from their couch. High ticket demand might not always be a thing and then you're stuck tarping sections.
Now the only place for expansion after this will be for the press box. As Central Iowa grows in population, (estimates put Des Moines Metro at 1M by 2050) more businesses will buy boxes.