Great point, and that made me want to take a look! As seen in the photo below, if you just plopped the NEZ right into the Horseshoe space and made it closer to the field, you would still have a LOT of space!
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And honestly, we could make the SEZ steeper than this and put things like the scoreboard, suites, etc. on top of it, which doesn't take much room as far as the ground level space goes.
When you account for the aforementioned suites and the assumption that we wouldn't want our stands to start like 30+ feet into the air (one of the worst things about the NEZ, by far), we could EASILY build something really cool with our current space. Again, this is just a drawing, but let's remember that these designs were released to the public in 2016, with apparently zero intention of altering Kirby at all:
And if you look at that first photo and compare the new SEZ stands to the rest of the stadium, it seems pretty clear that they planned on this structure being steep! And I hope we keep that idea!!