2)  I wanted ease of brazing, so a preload filler slot to be included.

3) Direct fitting of the brake outer casing with out silly ferrules to freeze in with corrosion and reduced kinking of the casing.

4) The gear outer casing ferrule to fit nicely into the CS stopper (a compression-less gear casing must use a ferrule)

5) I wanted a smooth rounded appearance so the stopper looks like it belongs being part of the tube, not like a plonked on after thought.

6) It must be stainless steel to  remove corrosion issues due to perspiration or collection of road grime.

7) It needed to cause no extra hassle time to be added to the construction process

Note:  I personally see no need for a slot in a road bike cable stopper because if the cabling is done correctly during assembly such as lubrication with “Slick Honey” or such, then there is no need to touch a cable until replacement is due. So, the inevitable paint chip from maintenance lubrication around the slot area is avoided.