[Too Many Projects]

With the extra strength of the extruded sides, I wouldn't be afraid to add an escape door. I'm sure the design has been engineered to account for the opening and those sides almost make the trailer a unibody with the frame. Looks like a heck of a trailer, but the website seems to be lacking a lot of detail, especially available options. The first option I would ask about is self leveling air ride. That alone will reduce the stress on the rest of the trailer, and your cargo, immensely. It could include an onboard, electric, compressor with a dump valve to lower the floor for loading/unloading.
The low-pro is interesting too, but it doesn't seem to include the car hauler. Too bad, as it would help with wind resistance and sway.
Yes, I believe you will like the increased stability of a 5th wheel attachment over the bumper pull.