Some buildings have circular ramps down to lower levels of parking but they'd probably have to sacrifice a fair amount of space to do that and they pretty much have to put the loading bays on the Market Street side.
I think it's a nice design. Hopefully the big glass convention room will look bright and active. The setback, public space, overhangs, and atrium along Argyle should work well. Certainly it'll be a lot nicer than the Herald Building.
The towers might be addressed somewhere in the presentation. There are a couple of photos in the video that weren't on twitter.
One other thing mentioned was the possibility of an international competition for some public art. I really hope that won't turn out to be more lighthouses. The Keltic Lodge view makes me wonder if that was the outcome of the Sydney session; from now on when you're sitting on a patio on Argyle you'll have images of Cape Breton beamed at you. I am dreading the fiddle music that will be blasted out along with it.