Stan, there's a good reason not to. The BAT +/- will be directly soldered to a 9V battery connector, the wheels and roller will be wires going to the track power. I'm not really saving anything significant by doubling up one wire, and I feel this is clearer as to what is happening.
For one of these that was assembled, I'm figuring that on one end the battery connector will be soldered and come out of the heatshrink envelope.
On the other end, two wires, perhaps orange and black, will come out for track power.
