Tony, you have a great little trailer there, and also a smart idea for adapting it and your layout to the realities imposed by the passage of time. I would make one observation however, and that is you may wish to modify the trailer a bit further to include an opening tailgate, possibly a drop gate / ramp combo so that you can make you modular sections roll in and out with board edge wheels. Barring that, you would at least be able to slide the modular sections in and out, without having to lift them up out of the depths of the trailers sidewalls.
Just a thought.