I did think of a potential issue with the whole "your spaceship doesn't move but the scenery looks like it is" idea. What about during takeoff and landing? Sure once you are already IN this proposed "travel dimension" that may work, but what about getting TO that dimension? You would still need to takeoff from a planet in your spaceship so maybe entities would still be needed until you reach Y: 1200. Not sure, just another issue that needs to be considered.