Hi Lewis,
Regarding the unused wires/terminals, it would make sense to have the reverse function available on the main control harness and also a lighting feed through the main harness to the rear light
(on the rear motors) to eliminate additional wiring going from front to rear.
Doubling up the battery feed and ground wires would also make better use of the unused wires provided that a 10 core cable is actually used.
As far as file format goes I can work with most standard file types. I use
Paint.net for the majority of my *.jpg drawings and TurboCad for the more involved
(or accurately detailed) CAD drawings, which can also import AutoCad *.Dwg files etc.
Alan