It is theoretically possible but not practical. If you look at my sketch, it will work but LOAD B must be completely isolated from chassis ground. That is impossible with most typical automotive accessories, radios, motors, lights etc. as they are internally grounded and use the chassis for return.
It would require that everything on the LOAD B side be a two wire circuit. Imagine the confusion five years down the road when you or someone else is trying to do some work on this circuit.
Might not be practical for much of anything beyond headlights, but some MCI buses came with that headlight system as stock in the early 1980's, according to those who know. In that case the wiring is reflected in the relevant schematic in the manual, I would assume. Your sketch and warning is 100% correct. In the case of my bus virtually all 12v loads are two wire, I used a "home-run" ground system and most everything is mounted in wood so there is no inherent chassis ground. Mind you, I power them from a Vanner and ground is tied to chassis ground at the bus bar. My headlights (1980 MC-5C) originally had 24 volt bulbs but there is now an MCI-sourced conversion box on each that converts 24 volts to 12 volts. It works really poorly and I need to figure out how to fix it or eliminate it. Splitting the headlights as I described is definitely an option, since I feel the total load is getting to be fairly high on the Vanner what with other possible loads as well, and another option is going back to 24 volt bulbs.