There's no reason that I know of why Jeep couldn't offer the XR + diesel. But for the time being, they simply don't.
Currently: Rubicon + XR + eTorque V6 + 8-seed auto OR XR + 392.
Soon: Rubicon + XR + ESS V6 + manual.
All three of the above are confirmed by Jeep. Will we get the XR on...
Pro tip: You don’t need an RTT to overland. Up until a few years ago, most overlanders didn’t run them. Try it with a ground tent first and see if you like it. The most experienced overlander I know still uses a ground tent.
Not knocking RTTs. They have many obvious advantages. But it’s not all...
Yes, I'd do LCAs at the same time. I would consider them necessary any time you're lifting the vehicle.
Make sure everything is tightened to spec post-lift. Installers can be quite sloppy about this. Loose bolts are the root cause of death wobble.