I can see where this thread, and other mentions around the web, would make owning an XV-JP seem like a dreadful idea. ☹
It's not, though . . . I'll second what was just implied: the balance between trail capability and cabin comfort is unmatched with the XV-JP. Unmatched to the point where it seems almost unfair to park with your fellow trail runners, climb in the back, turn on the lights and heat, open up the fridge to select your meal, crank up the stove and have dinner ready while the everyone else is still organizing the camp kitchens.
But the XV-JP is admittedly a better idea for one. Two rather friendly people can use it if most of their time unrelated to the palatial original bed is spent outdoors. But with only one person, you can (after a wee bit of modification) sleep on the bench without substantially deploying the roof. Lessening the roof opening is the key to making the cabin work in foul weather. Keep the roof closed or slightly ajar and problems of noise, heat retention, awesome clearance height, leaks and general tent integrity are hugely reduced.
But another way to optimize the XV-JP experience is to just not use it when its weaknesses will come out. On a still, warm and dry evening after a fun day on the trail, climbing into the original tent for a good night's rest under the stars was tough to beat. The problems come with wind, rain and cold. The original tent is too noisy in a high wind, too cold in low temperatures, too damp in substantial rain and unworkable in snow. Still, there are many workarounds, from earplugs to rain flies to better sleeping bags, that can create a tolerable situation.
Unfortunately, you still have the problem of perhaps needing to fold the dripping--and maybe even frozen--tent back up when it's time to move. Which one could correctly point out is no different than what thousands put up with using a rooftop tent, so why make such a fuss? Unfortunately, the difference is that the drippy XV-JP tent gets folded up INTO your living space, which is seriously hard to live with. One's willingness/ability to avoid frequently doing this is, to my mind, the biggest issue that establishes the line-in-the-sand, go/no-go workability of the XV-JP for any potential owner.
IF you can keep the roof largely closed in inclement weather because there's only one person sleeping in it OR because you don't take the rig out when the tent will get wet, the XV-JP is a great option. I assure you that having the comforts of a "mini-motorhome" while having the footprint and trail capabilities of a built Rubicon is very special and exceptionally fun.