IMO when you have a pop top roof on a vehicle it is to provide standing/living space within the vehicle interior and provision for sleeping. If you keep the roof and use the sunroof as the primary access point, you have a tent on top of the car and a car sized interior, the only benefit is that you can move between the tent and the vehicles interior without getting out, BUT once inside the vehicle what space do you have to go about your business? Getting dressed etc.
The thought of getting up in the morning and leaving my bed via the matterss doesn't appeal. If you use the ladder solution, then you might as well save the hastle and just bolt an Autohome Columbus Variant roof tent on top.
Still full marks for the effort and engineering involved, if you cut the full roof out the whole concept works far better.