Cool! It's a neat rig...definitely will turn heads.
For a short time, I drove a flat floor cabover years ago. Weird, not having the normal doghouse there, the motor on ours was angled over at 45 degrees.
A few random thoughts:
Climbing in and out of a cabover is not hard to do, of course, but if you are older, and/or physically limited, it could be a problem. Lots of on-the-job injuries of truck drivers were (and still are) caused just by exiting/entering the vehicle. I messed up a shoulder when I slipped one time...ouch that hurt! With this rig, you will be climbing in and out a lot, since there is no access (that I can see) between the tilt cab and the living quarters. If you have any problems like weak grip, bad hips, bad knees, arthritis, etc, it might become a chore.
IIRC, some of the Argosys had a rotating stair that swung out to help you get in and out of the cab, but I think that was the model with the 'set-back' front axle, and the stairs were forward of the steer tires.
Also, if you flat-tow a car behind that rig, get ready to have LOTS of stone damage to the front of the car, and maybe even some cracked windshields. Yes, you can add a stone guard like you see on the rear of large class A rigs, but this rig has a higher rear overhang and stuff happens. It would need a fairly long draw-bar, just to compensate for that long overhang negotiating bumps and around sharp turns. So trailering a car is the better option, but adds more expense, or just load the car in the back as it seems to be set up for that.
I'm going to guess that this rig gets about 6-8 mpg at around 65 mph, so fuel consumption might be a concern.
And of course, getting into and out of some choice campgrounds and boondocking off skinny forest roads might be out of the question.
But hey, it looks good once you get there!