I'm in a sort of similar situation, and have ground loops running around in my head after reading all the threads about the EG4 6500 EX.
I built a solar shed, the plan being to keep everything away from the house "just in case" I have 10kw worth of panels, ground mounted on 2" posts, 2 per post. Why? Because my initial testing involved having them track individually. The plan is to have the 2 6500EX feed to a new panel in the shed, and then from said panel back to the house to an external 50a plug. There is another 50a gen input on the house, to a Reliance 50a generator panel with critical loads wired to it. The Reliance panel could either be fed by the grid, the gas generator or the solar this way (2 foot cable from female 50a plug from solar shed to 50a gen plug). The resultant ground screw, and grounding conundrum is making my head spin....the Reliance panel not having the neutrals switched just adds to the issue. The 6500EXs will NOT be connected to grid power in any way.
Basically want to be able to run critical loads off of solar until they can't, then switch back to grid until the batteries are rejuvenated. With the individual switches in the Reliance panel it's nice as you can switch loads individually as your solar capacity allows. Final plan is to go completely off grid, but electric stove and water heater make this a daunting task.
Sorry I rambled, any thoughts would be appreciated.