On the Detroits there is no way to isolate the blower from the engine. The air box from the turbo goes directly to the inlet of the blower and the blower is gear driven off the front accessory drive. If the blower was somehow dropped out of the picture then the vanes ended up becoming a big restriction for the turbo to overcome. Whatever the reason GM decided to add a turbo to feed the blower it obviously worked but on the surface it seems like the induction system was more complicated than it needed to be.
Mike
