Wasn't there a plan in the 90's to build a dome at McCormick Place called the McDome? That may be the one ok place to build a stadium in a city because you can share parking with McCormick Place and use the dome as part of the convention center.
I have to imagine there are limited tailgating options at Soldier Field. It's also the smallest stadium in the NFL so if parking is adequate, would it be adequate for 10,000 more people?