From a floor plan perspective, the CN Tower would probably make a great residential. It's quite shallow from core to exterior walls which means suites get a great deal more glazing per sf than the more modern rectangular towers with large floor plates. It's floor to floor height - at 14 feet if my memory is correct - also provides the ability for higher ceilings. I don't know how the numbers would pencil today but from a design perspective it would be a fabulous opportunity to create something quite iconic and special.