If Hattrick is as close as an example to how attendance works in BB, then there would be a set amount of fans willing to attend the game. This amount would act as a cap, and the distribution of the fans would be a certain percentage of each seat type. Given that scenario, it would be impossible to sell out lower tier seats if the proportion of lower tier seats was greater than bleachers, not to mention the loss of income from not selling bleacher seats that would have sold if the seats existed. I'm sure modifications must have been made to how attendance works in BB. For example, ticket prices and PR manager having an effect on how many fans show up to the game. But I'd be surprised if the basic idea of max percentages of fans for each seat type had been removed.