We seemed to have drifted from SDS to falling into the hot tub thread.
As for the last question, since all of this equipment seems to be grouped, I see no problem with bonding everything to the neutral bus in the service disconnect enclosure.
The handbook makes lots of references to building steel but that is not our electrode here. For the example of a water pipe electrode they show a GEC snaking through the building that all the transformers are tapped to. (exhibit 250.25) In our case, simply tapping it at the grounding bus seems to be a far cleaner installation and meets the intent of the code. Everything will be grounded to a single point.
