Thinking a bit out of the box regarding where the Art Institute might build it's new wing...
Does the School of the Art Institute of Chicago actually need to be in main Art Institute building?
It occurs to me that
they already have a bunch of programs and facilities located in the loop within 3 or 4 blocks of there, and that there is a lot of loop office space in need of creative reuse these days.
If SAIC were given some of that money to rehome itself in former loop office space, then that would free up plenty of room for a new wing on the south east corner of the museum. And not having to build over the tracks would likely make it simpler and more affordable...
I'm honestly not sure if this is workable. Maybe the SAIC gets too much benefit from being right there in the museum, or it's wing of the building is itself worth saving, I don't know.