CanBack Side Mount Rack Uses?

CanBack is prototyping a side mount rack system for their canvas camper shell. The rack system is not online yet, but it probably will be before this Labor Day weekend is over (www.can-back.com)

It will be available in half-length, and full length systems, as well as a single top or bottom rail, and single vertical rail.

Each groove will accept 1/4-20 threaded inserts. Plates can be made for any threaded stud diameter of any length, or any threaded hole size. Each vertical rail can be slid to any position, and additional vertical rails can be mounted to the horizontal rails.

This is the Half-Length system. Full length systems will have 5 vertical rails.

The question is: If a universal side mount frame system was available, what specific accessory mounting systems would you like to have available to attach to the frame?