The rear caliper design was a common ATE caliper in the day. Used in other applications including the Ferrari 308. Leader screws are in the wrong spot, down low, when mounted on the 914 trailing arm. But they bolt right on, and allow you to run a vented rear rotor.
The design was fine, the years have not been as kind. Hindsight is always 20/20. Unfortunately the caliper was not in production to go through a redesign.
While yes they should have just did the 911 e-brakes on the 914, sad to say they did not. Lucky that is an easy fix with a welder and a few parts.
That being said, the last time I dealt with a 914-4 rear caliper was in the 80s on my Karmann Ghia