Good point about the click box.
Yes you don't need a cable stop. But I have still fitted one on my sram bike. From what I remember:
1) Its to act as an adjuster with a spring fitted in a join in the outter. I have brifters so I have no adjustment at lever.
2) The spring increases the cable return to get the lower gear. Which initially I struggled to get in addition to the high gears on the IHG.

Not sure if need the cable stopper but I got it to work by adding it, therefore I am leaving it alone! I will upgrade the outer at sometime.

You will need to address cable friction in mezzo's long and winding routing. I strongly recommend teflon inners. Teflon lined outers idealy also.

I have started to add washers routinely now in all my cable outer terminator now. I find that often cables has pulled through these, more frequently. So I add tiny brass spoke washers.