Jane Jacobs criticized the "cultural zone" concept in planning as well. They tend to become isolated and dead when nothing is happening. Yet every American city seems to have one. Everything is very clean and polished and the architecture is sophisticated but it ends up feeling very contrived, sterile, and typically dead.
We also aspired to building something like that in the St. Lawrence area, hence the reason for all the demolition that happened there. Those disturbing photos of huge parking lots where Victorian blocks stood are quite memorable. In the end only the St. Lawrence Centre was built.
For me, the idea of more cultural institutions at the Ex interspersed with mixed-income high density housing, commercial, and light manufacturing (small scale luxury products that could attract curious visitors) is enticing. I'd also consider connecting every street from Liberty to the Ex, so that artists and businesses serving the institutions at the Ex could also find property at Liberty. As I said above, it would be difficult to pull off but there has to be more that could be done with the Ex grounds and it should be something that would keep it a unique place in Toronto that could draw a lot residents and tourists all year round.