What I don't understand about this bowl shape is that there is so much wasted space between the athletics fans and the tracks both top and bottom. Those stands could be permanently altered to give a shallower rake and bring the stands to just next to the running track.
Then, behind the goal posts, the rake of the lowest tier is made shallower, and the new section of the track be made retractable/dismantleable. I understand this lowest tier already has a fairly shallow rake, but at least the expanded stand wouldn't have zero rake at all. For the athletics then, there would be a wall behind the bends. There would still be some distance behind the goal, but nothing like what it is now, in fact, it would be half.
The biggest issue is therefore the rake of the lowest tier. Making a shallower rake on an existing structure is easier than making a deeper rake, for instance, so it could be just a matter of building up the concrete on the terrace in a controlled way.