Hi,
The asymmetry is so that there can be an aisle to get in from the back door. Also, since the driver in in the center that seat can be moved forward, and that ripples back through the seating plan. The tapered sides make it very hard to fit seats side by side -- even if they are staggered. The seat on the right side is staggered and no additional seats could be fit behind it.
Yes, the hatch will require reinforcing, but it would be in the car even with side doors, and the most likely crash impact zones are the front and sides. Your point about the Loremo is apt -- since that car was very low, and they also wanted to surround the passengers with a continuous structure, they were left with the option of (essentially) entering through the roof. The CarBEN entry is through the rear transom and the roof; since the height limitation is not as restrictive.
There will be at least one "hoop" of a roll cage just behind the driver, and it will be supported by two tubes that run from the floor up to the roof. Another advantage of no side doors is the window pillars only span the windows themselves, making them much stronger than in most other cars. So the roof on CarBEN will be quite robust, I think.
Think about the 'B' pillar on a typical 4 door sedan: it alone spans from the floor to the roof, with no stiffening panels. In the event of a side crash impact, that one pillar takes virtually all of the force. Even with the anti-intrusion bars in the doors, the force exerted on them transfers as point load onto the 'B' pillar.
The anti-intrusion bumpers (there are probably going to be two) in the sides of the CarBEN are continuous all the way from the back of the car on one side, around the front and continuous to the back of the other side. These will be supported by the roll bar(s) up over the roof, and the front will have a subframe crush zone. The floor will have to be a box beam, around the battery pack and this supports the base of the roll bars.
Here's some images of the battery pack I modeled today (all 768 cells!):
This would be about 55kWh! :-O I'm thinking a few cells cane be moved from the very back and added to the side flanks? Or, I'll worry about the exact layout when I get the chassis built...