72-104 allows USEI and you could treat each distribution centre as a service. It would be tempting to do this because of the issue of different potentials between ground and neutral over distances (and cable cost). If you ran ACWU with a separate ground, I'm not aware of any rule requiring a disconnect at each building where it isn't a service.
Perhaps the inspector wouldn't comment on design issues because the inspectors don't agree on whether a main disconnect is required on a sub-panel where the sub panel is in a separate building and this is similar.
Be aware that entrance switches can't be in public areas unless "adequate precautions are taken to prevent interference", under 188.8.131.52 of the National Building Code of Canada.