Sounds like a case of 'and now you have two problems'. The proposed solution addresses a problem that doesn't practically exist (few people, once they learn the meaning of the buttons, are confused about their function) by making elevators more inefficient by removing the directional call. Taking away the elevator position display also removes the elevator's progress indicator so on top of elevators now being slower for everybody, you can't estimate how long you might have to wait for one. Seems more like UI pessimization.
Indeed the proposal is not UI simplification since you reduce the action of pressing one of two buttons with the action of pressing one button and then read direction for each elevator which stops after your pressed the button.
Having people make choices based on information they have to read should be avoided when possible.
