All I can really think of is add some aisles running radially out from the center and then add some sort of viewing podium a la the Roman ceasars. The wealthy will sit near the ceasar guy no matter what then. Might want to add in some tiny steps along the aisles and maybe some tunnel cuts for going to the "concession stands" or restrooms beneath the stands. I've always wanted to do a stadium so I'll be watching how you come along on this.