The latest patent filtered by the patent office correspond to Hyundai and your last idea is applicable to vans. Sketches leaked that show us a new idea opening doors for van, with many practical advantages. The concept is based on a door opening to the side, kind gullwing, which are complemented with a pair of sliding doors traditional.
The advantages of these doors gullwing patented by Hyundai are clear at the time of access to the vehicle or trunk, as it leaves a completely open space that facilitates especially the enter and exit of passengers. You can also have great utilities to vehicles, camper, leaving free access to the interior of the os serving as a kind of progress or porch when camping.
To overcome the main disadvantage of the system is the sliding door traditional, that is integrated into the gate-type gull-wing. The advantage of sliding doors is that they open up in places very narrow with little or no space, something that would be unfeasible for the door liftable large dimensions of this idea. With this duplication of doors, ensures the versatility of the concept in all kinds of circumstances.
The idea on paper is really appealing, but applying this type of solutions would have a very high cost. We do not know which are the intentions of Hyundai about it. The main problem of this type of door would be its heavy weight and its technical complexity, apart from that it would be an expensive system to produce, and therefore, of purchasing. Would be at risk its viability.
Leave the rear open, you can first submit a risk of structural weakness for the vehicle, since there is a lot of surface that has no pillars or other elements to provide increased rigidity to the assembly. would have to reinforce both the low as the roof of the vehicle to compensate for the lack of rigidity, and that would mean a greater weight. The door gull wings would be in addition to very heavy and would need some type of assistance for the opening and closing. The visagras in the ceiling for these doors would also have to be very strong and heavy. These weight increments in the high areas would impair the center of gravity of the van and its dynamic behavior.
Source – Autoblog