Found a slightly different way to emulate a working inner door.
Its a sliding door that comes down while the elevator has a delay. When the door covers the entrance, the elevator delay finishes and moves along with the inner door on the way down at the same speed giving the illusion that the inner door is attached to the main elevator.
With 3 key points it is probably doable to have the door look like it only opens/closes from the top of the elevator(Right now I have it follow through so it comes from top[of the elevator] then proceeds through the floor of the elevator at the end of the keypoint path and the opposite way on the way back up(Through floor into ceiling when elevator stops.)
Its not ideal as it will only work with vertical doors (The two movers must move parallel to create the illusion, not perpendicular or else the player will notice the texture of the door panning) and a 'proper' solution would still be appreciated if anyone knows of one.
Update: This seems to have problems when tested online. In single player I can get the doors to sync up perfectly. However when put on a dedicated server, the speed of the movers changes and they outpace each other ruining the effect.