Shift/Brake Cable Modular Hookups

Okay, this is very specific. I have a few bikes, & since I'm cheap & I gradually build up more bikes, I have been moving parts from older bikes to newer ones. One of the most painful things to redo is the handlebars: there can be a mix of brake systems (cantilever/dual pivot) & brifter/bar end shifter systems.

The underlying problem is cable housing lengths. For bar end shifters, I prefer to run the cables under the bar tape. Well, if I switch to brifters (already mounted as brake levers), th