On my frame the internal routing "ports", the things that are screwed into the frame with a small hex-head screw, have ingress/egress holes large enough for cable housing to pass through it. Is there a variant of these screw-ins that has a cable-stop, so bare cable could be used? A bare cable would be easier to install and a handful of small cable donuts would keep things quiet. Do these things have a name?
They aren't universal in any way. Depending on the bike/brand, there may be some out there that fit the same frame hole and do what you suggest in the case of a manufacturer trying to employ the tactic of re-using the same small parts, but that's not how it usually is.
Some frames are set up to allow a straight shot of cable like you suggest, but usually it would have that sort of housing stop if so. Running bare cables in a frame set up for continuous housing is generally not something that can work.