I guess the method depends on how accurately you want to represent the cables.

Is just a line good enough? Or do you want to show the cable gauge? What about the end connectors?

I'd suggest making a single CATPart in your assembly for all the wires. And then just make Point-Point lines between the connecting centers of the other parts. (this will make external reference links to the other parts)

If you want to show more than the lines, then use a RIB feature.

If you want the connectors, then PowerCopy would be the quick and dirty way to duplicate them. Or setup a catalog.