My logic has taken me full circle to where I can better appreciate what dnix71 has suggested. If the generator and inverter will be used in multiple scenarios, from a human-factors engineering viewpoint, it doesn't make sense to set up a system that requires configuration perfection of the source each time one needs it for temporary backup power. Either a transfer switch, which provides the "essential bus" I referred to earlier, or running cords, which is electrically the same as the transfer switch, are the only methods that I can envision being suitable for temporary backup power. That enables the grounding method to be automatically controlled by the source's current grounding configuration, rather than requiring the source to be configured perfectly to match the load's grounding method each time it is deployed, to prevent destroying equipment or creating an unsafe situation. That method also greatly expands the number of devices suitable for temporary backup power to almost anything out there, which is something that dnix71 mentioned, but took me a while for me to fully appreciate.
Using a second 240V breaker with mechanical lockout that I mentioned earlier, would be more suitable for a permanent standby power installation where the source could be configured one time to match the load's ground configuration. This method also restricts the number of suitable devices to those that can optionally utilize a bonded neutral.
This discussion gave me a much needed broader perspective as to why the transfer switch/cord strategy is heavily favored for temporary emergency power setups, and might alter my strategy.
Thanks!