The 2D drawing looks way cool. If it were build I would think it would be for an expedition type rig.
All 4 door rigs I have seen regularly on the more difficult trails have a problem with the back door opening up when the body is flexing. This is after years of wheeling though. The Jeep Cherokee and the Ford Centurian come to mind. I have never seen a 4 door LC (FJ60, FJ80) rear doors pop open. I would look at those to see how they are structurally built.
All 4 door rigs I have seen regularly on the more difficult trails have a problem with the back door opening up when the body is flexing. This is after years of wheeling though. The Jeep Cherokee and the Ford Centurian come to mind. I have never seen a 4 door LC (FJ60, FJ80) rear doors pop open. I would look at those to see how they are structurally built.