The only issue with that is you need the height at the feet like you get on the J30 and you also need the shell height to hold the mattress/tent fabric so the tapered front is an issue. There is a reason John did it the way it is. I own one and know the challenges of it. The AEV version, like yours, looks way better but would not function as fabricated. The foot room and the front window on the J30 are the best feature. I have had to sleep with my head towards the drivers seat a few times.
I do think the J30 could go on a diet and get some of the 6" back. The J30 could get rid of the false ceiling in the top to gain some space, but it would not be much and would loose the luxury feeling inside. Or tapper the mattress at your feet I guess but loose the option to sleep the other way around. I think the best option would be to recess their mounting points to gain an inch, but would make the fabrication trickier.
Doing a mechanism like the J30 is a fallback position for this one, but I think it's worth prototyping it as I've shown it to see how the room inside really works out. Both the J30 and the AEV unit have something taking up room that this design doesn't - the roof/false floor. My plan is to mount the sleeping platforms directly on the sport bars, which saves quite a bit of space (and weight) over that those others have. That additional space should also be enough for the mattress/tent fabric as you mentioned.
I would love it of Ursa Minor made this barn door. They have the skills and equipment. I am sure my flip up window will break one day. I have the AEV tire carrier with fuel tanks and people always try to close the tailgate without the window all the way down or the jeep is parked on a hill and it closes itself. It has almost shattered way to many times.
I'm not a J30 owner, but I have had a barn door on my LJ Safari Cab for almost 4 years now, and based on that experience it seems to me a barn door would be highly preferable to the factory lift glass in a camper situation.
If some company other than Ursa Minor signs up to bring the barn door to market, you'd still be able to use it with the Ursa Minor, it's completely compatible and can be installed with no modifications to the Ursa Minor. If there was an Ursa Minor owner who lives close to me who wanted to do what Tom did (put in some sweat equity working alongside me to make one), we could do one and get it installed and tested with the camper.
EDIT: Before I get a bunch of messages from people living far way who want to drop by for a day or two to make a barn door for their Jeep, it really isn't something you can come by to start one day and drive out with it finished the next. There are a lot of man hours and process time hours (example: waiting for gelcoat to cure as the first step of the layup, before the fiberglass layup can begin), so it's something that takes a bit of time - that's why I wrote "an Ursa Minor owner who lives close to me"... molding, assembling and finishing a barn door is best done in a series or work sessions, which is hard to do if someone lives far away. Installing a finished barn door doesn't take very long, but doing all the work to get there takes a bit of time.
The Safari Cab tilt-up canvas would differ in a few dimensions and some details from the trailer version, but overall it would be very similar. Having proven it on the trailer, I'm confident it would work very well on the Safari Cab as well.
