I hear what you are saying Charlie. If the OP is a hardcore boondocker, I can see some benefit. For a campground and getaway user that just doesn't want to deal with propane, not so much.
My Onan pulls from my main tank and the pickup is above 1/4 tank. I would really like to add a 2000i and then I would have very flexible and fuel efficient power options. Even the 2000i could operate induction cookers, electric heater, etc. Only A/C would really need the big boy.
I think boat forums would be really good to look at, since they have very specific reasons for wanting to be all diesel and would be most experienced in the +/- discussions.
Jose