I have not worked on gen 1 for many years, but found mine to be glued shut, so I had to cut mine open. (then re-glue them shut).
As you can see from this photo (in my photo gallery at upper right) I did run several light switches, a horn button, and other accessories up thru the control shaft and to the handlebar.
In this photo you can also see my bike computer, as I had added a magnetic pulse counter to one wheel, which gave me speed, odometer, and many other functions. I also had temperature sensing on this unit, so that I could maximize range by not letting my NiMH batteries get too hot or too much hotter than the ambient temperature.
I also had a rear view camera with monitor on the left hand grip, but you cannot see it well in this image.