The differences between an 80,000 and a 22,000 capacity athletics stadium are enormous.
I recommend that the designers and contractors play with that most versatile of toys, Meccano, for a while. They might then get a few ideas that would allow them to fulfil the three F's: function, form and flair - in that order - without recourse to a demolition and reconstruction exercise.
They might even have enough reusable material to build two more smaller stadiums.
James R Knight (F ret), 4 Jacobean Road, Lincoln LN6 3RB