So responding to the feedback that the lack of knowledge about your destination and current situation, with other things, make the rider feel claustrophobic or not in control... why not incorporate a system that many of us will be used to seeing in Trains or Trams. Picture a screen on the inside of the elevator with a list of stops the elevator will make based on the riders it has picked up. At the top of the list is the next stop with the time to arrival, listed beneath that is each other stop.
I'm making two assumptions with this, the elevator won't necessarily run a linear route, it may determine the fastest way to get all of the requesting riders to their destination is, for example, go up ten floors, drop off a rider, drop down three floors, pick up an upbound rider and a downbound rider, go down three floors for the downbound rider and then finish the run for the upbound riders. The display would indicate the order of floors and show each upcoming stop.
Second, I'm assuming there's no conceivable way there will be hundreds of stops on the screen at one time. I'm thinking around a maximum of 21 displayed. Next stop at the top and two columns of ten beneath it. Other interesting details may be displayed such as current speed, current direction, etc.
I like the keyed in destination approach and feel like it will be shorter input than any other manual method.
I'd also like to suggest a system where riders in a building have a key card which links with their calendar and can take a user to the floor they're expected on with a swipe of the card. Manual entry would always be an option. (The assumption here is this is an office building.).
I like the idea of voice commands but... you've all seen this, right? https://www.youtube.com/watch?v=KjOEokudZs4