If they could just cut half the height of the classic boxes it would already be a big improvement. Especially since most of the animals spawn on the ground level anyway.
It is just meters of dead space in most of them, and there really aren't other options for that than to make your building that height, which isn't a very logical base height for anything.
We used to have the same issue with the shops but now we have had the box-free versions for around 2 years, which has been such an improvement. And clearly, they can work without being four meters tall, so I wonder why the exhibits can't. I can see why changing the width might be complicated, since the interior design, spawn spots for the animals, and keeper interactions all depend on this. But in most of the designs, especially with the desert-themed ones, nothing important is taking place in the upper 2meters