QUOTE
it's just a sheet of material over the mechanics?
What did you think was in there? Until jus a few years ago there was not much consideration to any kind of crash protection from the side, anyway. Anything in there now must still allow for the "mechanics." Again, the sheet metal on most vehicles is 'deformed' from a flat sheet because it would otherwise have very little strength. Curving a sheet in even one direction will give it amazing strength an opposite direction. Create complex curves, in two directions and that sheet will withstand forces from just about
any direction. The designers job is to make these curves satisfying to as many people as possible.
For example, curve/curl a sheet of metal (or paper) so that it does not lay flat on a surface. You can now put quite a bit of pressure on the curved sides of that material. However, take that same flat sheet of metal (paper doesn't work to well since it is not very 'malleable' when dry, and stamp it into a concave shape. It will now be quite hard to bend, twist, or flex. Or, take that sheet of paper we were plainly with earlier and roll it into a tube. Secure it with some kind of tape or glue. You now have a 'fuselage' that is quite strong in the axis running through the two open ends. But it is still very easy to smash that tube flat because there is no strength in that direction.
I would be confident that the people who designed this 'door' mechanism are smart enough to know the real requirements for strength and how to build the device safely, if not inexpensively. Otherwise, they are fools and will be found out quite soon. They have to do more than sell these things, they have to perform many different types of tests and publish the results for any government that might allow sales in their country. I would have no fear of driving one of the
production models when and
if they ever get built. Buying one is a completely different decision, one based on need and ability
not safety!