That's pretty cool!
Random thoughts:
Strap - no big deal. Wouldn't worry me more than tie down straps etc as others have pointed out.
I didn't see - are the panels plastic or fiberglass? If they are fiberglass, it gives the builder the option of glassing the panels together permanently for extra rigidity and sealing. The modularity is still a feature for inexpensive construction and shipping - so I still see that as a big plus! I could even see the utility of hardening the outer shell and keeping the interior modular.
Pop-top roof - I'd definitely switch to a hard roof. I don't have any strong feelings about the sides of the pop top though. Canvas, hard panels both have their strong points. Heck - could even do it in screen material and think of it as the world's biggest ceiling vent!
I would also recommend having an additional widening panel available. Speaking for myself - I'm 6' tall and beds under 80" head-to-toe are fairly uncomfortable at best. The other advantage is that 80" also allows the user to use standard home mattresses should they choose.
Another suggestion would be to look into possible dual dinette floorplans that allowed a permanent bed along with a 2 person dinette. That is a very popular configuration among the fiberglass RV crowd for obvious reasons.
I suppose if I were to lay out a preferred arrangement it would be: permanent 80"x60" bed, two person dinette (possibly against the wall), privacy room (for portapotty) plus convenient storage and counter space.