Take out some bleachers in premium spots and put in seats.
Take out all benches and replace them with new benches and back bars. Increase the space between seat numbers, so we all have a little more room.
Fill in the corners to offset the loss of capacity from the new seats and new benches.
Put a facade on so it looks like a stadium, not big bleachers. The facade can be any number of things and doesn't have to break the bank.