Great write up again
1 car is driven by politicians, the other by drug dealers and yummy mummy's. I've always loved the RRS and I think it compliments the xk perfectly.
I'd admit that economy is pretty dire but to be expected in something so big and heavy. You clearly work hard and you only live once. You just need to fill it with little nuts now.
My mrs likes 4x4s and she has had them for the past 6 or 7 years now, never a RRS despite her pestering. It's really liberating knowing you can drive anywhere or do anything in the car and it swallows up tonnes of crap and kids in the process. We used to spend a lot of time outdoors and go places you wouldn't have to worry about the simple things like dirt tracks, potholes and even parking in damp fields and grass verges.
As you say the new model is much lighter, carbon body or something? Should make a huge difference to drivability and economy.
On another note, I'm frankly amazed your mrs would even let you consider chopping the RRS in for something else, she must love it.